Add texts to the icons on the toolbar

The toolbar follows the system style to display texts associated to
icons. Since no specific text is provided, the text used for the action
associated to the button will be used. This could make some of the
buttons rather big.

Add short texts to the icons so that each button uses a reasonable
amount of space.

src/mainwindow.ui

@@ -145,6 +145,9 @@
    <property name="text">
     <string>&amp;Add torrent file...</string>
    </property>
+   <property name="iconText">
+    <string>Open</string>
+   </property>
   </action>
   <action name="actionExit">
    <property name="text">
@@ -158,6 +161,9 @@
    <property name="text">
     <string>&amp;Options...</string>
    </property>
+   <property name="iconText">
+    <string>Options</string>
+   </property>
   </action>
   <action name="actionAbout">
    <property name="text">
@@ -168,16 +174,25 @@
    <property name="text">
     <string>&amp;Resume</string>
    </property>
+   <property name="iconText">
+    <string>Resume</string>
+   </property>
   </action>
   <action name="actionPause">
    <property name="text">
     <string>&amp;Pause</string>
    </property>
+   <property name="iconText">
+    <string>Pause</string>
+   </property>
   </action>
   <action name="actionDelete">
    <property name="text">
     <string>&amp;Delete</string>
    </property>
+   <property name="iconText">
+    <string>Delete</string>
+   </property>
   </action>
   <action name="actionWebsite">
    <property name="icon">
@@ -192,6 +207,9 @@
    <property name="text">
     <string>Add &amp;link to torrent...</string>
    </property>
+   <property name="iconText">
+    <string>Open URL</string>
+   </property>
   </action>
   <action name="actionCreate_torrent">
    <property name="text">
@@ -316,6 +334,9 @@
    <property name="toolTip">
     <string>Lock qBittorrent</string>
    </property>
+   <property name="iconText">
+    <string>Lock</string>
+   </property>
    <property name="shortcut">
     <string notr="true">Ctrl+L</string>
    </property>