[Icons] - Use theme icons when possible & divers KCM modules

Created by: scachemaille

Use theme icons when possible #62

• changed to use theme icons when possible, if no themes icon available it will fallback to the hard coded icon, or the fallback theme
• When manjaro-settings-manager-gui is launched with pkexec, it will use the hard coded icon, because Qt don't know the icon theme when launched with pkexec. the theme icons used are:
  1. list-add
  2. list-remove
  3. view-refresh
  4. draw-arrow-back
  5. dialog-ok-apply
  6. gtk-quit

KCM modules

• Hide restore button in keyboard module page (the module button already have the functionality)
• Hide restore button in keyboard locale page (the module button already have the functionality)
• Add default and apply button in Time date module, there was no possibility to apply change beside the dialog when we quit

For the icons It need maybe some test on exotic DE/themes with and without pkexec