Use default values for inconsequential fields

Or when the default value is actually what we want.

src/gui/optionsdialog.ui

@@ -1570,9 +1570,6 @@ Manual: Various torrent properties (e.g. save path) must be assigned manually</s
                  <property name="text">
                   <string>Maximum number of upload slots per torrent:</string>
                  </property>
-                 <property name="checked">
-                  <bool>false</bool>
-                 </property>
                 </widget>
                </item>
                <item row="2" column="0">
@@ -1580,9 +1577,6 @@ Manual: Various torrent properties (e.g. save path) must be assigned manually</s
                  <property name="text">
                   <string>Global maximum number of upload slots:</string>
                  </property>
-                 <property name="checked">
-                  <bool>false</bool>
-                 </property>
                 </widget>
                </item>
                <item row="2" column="1">
@@ -1668,9 +1662,6 @@ Manual: Various torrent properties (e.g. save path) must be assigned manually</s
                    <property name="enabled">
                     <bool>false</bool>
                    </property>
-                   <property name="text">
-                    <string/>
-                   </property>
                   </widget>
                  </item>
                  <item>