Renamed DispVM and "Is DispVM template" for more readability

Replaced instances of "Default DispVM" and "Is DVM Template" with
more readable "Default Disposable VM Template" and "Disposable VM Template"
respectively. Added tooltips.

fixes QubesOS/qubes-issues#4935

ui/globalsettingsdlg.ui

@@ -88,7 +88,7 @@
       <item row="4" column="0">
        <widget class="QLabel" name="label_8">
         <property name="text">
-         <string>Default DispVM:</string>
+         <string>Default DisposableVM Template:</string>
         </property>
        </widget>
       </item>

ui/qubemanager.ui

@@ -238,14 +238,14 @@ in backups</string>
       </column>
       <column>
        <property name="text">
-        <string>Default
-DisposableVM</string>
+        <string>Default DisposableVM
+Template</string>
        </property>
       </column>
       <column>
        <property name="text">
-        <string>Is template for 
-DisposableVMs</string>
+        <string>DisposableVM
+Template</string>
        </property>
       </column>
      </widget>
@@ -258,7 +258,7 @@ DisposableVMs</string>
      <x>0</x>
      <y>0</y>
      <width>1100</width>
-     <height>28</height>
+     <height>23</height>
     </rect>
    </property>
    <property name="contextMenuPolicy">
@@ -853,10 +853,10 @@ DisposableVMs</string>
     <bool>true</bool>
    </property>
    <property name="text">
-    <string>Default DisposableVMs</string>
+    <string>Default DisposableVM Template</string>
    </property>
    <property name="toolTip">
-    <string>Default DisposableVMs</string>
+    <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Default DisposableVM Template&lt;br/&gt;&lt;br/&gt;Which qube should be used by default as a template for DisposableVMs started from this one? DisposableVMs will inherit their template's configuration and installed programs.&lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
    </property>
   </action>
   <action name="action_is_dvm_template">
@@ -867,10 +867,10 @@ DisposableVMs</string>
     <bool>true</bool>
    </property>
    <property name="text">
-    <string>Is Template for DisposableVMs</string>
+    <string>DisposableVM Template</string>
    </property>
    <property name="toolTip">
-    <string>Is Template for DisposableVMs</string>
+    <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;DisposableVM Template&lt;/p&gt;&lt;p&gt;&lt;br/&gt;&lt;/p&gt;&lt;p&gt;Allows using this qube as a template for DisposableVMs. The DisposableVMs will inherit the VM's state (configuration, installed programs etc.), but their state will not persist between restarts. &lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
    </property>
   </action>
  </widget>

ui/settingsdlg.ui

@@ -808,8 +808,11 @@ border-width: 1px;</string>
             </property>
             <item row="5" column="0">
              <widget class="QLabel" name="label_26">
+              <property name="toolTip">
+               <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Which qube should be used by default as a template for DisposableVMs started from this one? DisposableVMs will inherit their template's configuration and installed programs.&lt;br/&gt;For a qube to to appear in this list, it must have the &amp;quot;DisposableVM Template&amp;quot; checkbox enabled. &lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+              </property>
               <property name="text">
-               <string>Default DispVM:</string>
+               <string>Default DisposableVM Template</string>
               </property>
               <property name="buddy">
                <cstring>default_dispvm</cstring>
@@ -817,7 +820,11 @@ border-width: 1px;</string>
              </widget>
             </item>
             <item row="5" column="1">
-             <widget class="QComboBox" name="default_dispvm"/>
+             <widget class="QComboBox" name="default_dispvm">
+              <property name="toolTip">
+               <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Which qube should be used by default as a template for DisposableVMs started from this one? DisposableVMs will inherit their template's configuration and installed programs.&lt;br/&gt;For a qube to to appear in this list, it must have the &amp;quot;DisposableVM Template&amp;quot; checkbox enabled. &lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
+              </property>
+             </widget>
             </item>
             <item row="6" column="0" colspan="2">
              <widget class="QPushButton" name="boot_from_device_button">
@@ -862,10 +869,10 @@ The qube must be running to disable seamless mode; this setting is not persisten
             <item row="2" column="0">
              <widget class="QCheckBox" name="dvm_template_checkbox">
               <property name="toolTip">
-               <string/>
+               <string>&lt;html&gt;&lt;head/&gt;&lt;body&gt;&lt;p&gt;Allows using this qube as a template for DisposableVMs. The DisposableVMs will inherit the VM's state (configuration, installed programs etc.), but their state will not persist between restarts. &lt;/p&gt;&lt;p&gt;Setting this option will cause this qube to be listed as an option in the &amp;quot;Default DisposableVM Template&amp;quot; dropdown for all other qubes. &lt;/p&gt;&lt;/body&gt;&lt;/html&gt;</string>
               </property>
               <property name="text">
-               <string>Allow starting DisposableVMs from this qube</string>
+               <string>Disposable VM Template</string>
               </property>
              </widget>
             </item>