Added settings dialog

Added platform specific settings storage/retrieval

FossilOrigin-Name: 66205d14199523228d7f6fa0241a7ef7162f6940

CommitDialog.ui

@@ -2,6 +2,9 @@
 <ui version="4.0">
  <class>CommitDialog</class>
  <widget class="QDialog" name="CommitDialog">
+  <property name="windowModality">
+   <enum>Qt::WindowModal</enum>
+  </property>
   <property name="geometry">
    <rect>
     <x>0</x>
@@ -13,6 +16,9 @@
   <property name="windowTitle">
    <string>Commit</string>
   </property>
+  <property name="modal">
+   <bool>true</bool>
+  </property>
   <layout class="QVBoxLayout" name="verticalLayout">
    <item>
     <widget class="QComboBox" name="comboBox"/>