Fix command-line selection of setting panels when in 'Normal' user mode.

If you were in Normal mode, and right-clicked the panel, and call panel settings,
if would bring up the wrong page in cinnamon-settings.
Fix gtk 3.4-incompatible property on gtkentry box
Make c module warning more helpful
cinnamon-settings: Use introspection instead of ctypes to load
cinnamon-control-center modules
Merge pull request #1653 from mtwebster/settings-fix

Fix command-line selection of setting panels when in 'Normal' user mode.