Merge lp://qastaging/~dpm/ubuntu-filemanager-app/merge-settings into lp://qastaging/ubuntu-filemanager-app

Merges the view options and the current settings view into a single settings page.

Merges the view options and the current settings view into a single settings page.

I've done some cleanup and removed some dead code. However, one related thing that still needs to be fixed is how settings are stored and the UI updated when they change. I see two issues with the current code:
- Settings are properties of either MainView or the FolderListPage component. This makes it a bit unwieldy to set from the Settings page. They should all probably be properties of one single component.
- The way to put settings into effect once they've been changed from the Settings page is to use the reloadSettings() function. Is there a more efficient way to trigger an update of the properties?

Any feedback will be really welcome!

Notes:
- Not an issue, but the use of a dark theme triggers bug 1389112 (UbuntuShape shown for ItemSelector)
- Not a big issue, but again the use of a dark theme triggers bug 1389115 (ItemSelector ticks not visible)
- Wrapping the settings into i18n.tr() is not a good idea, as if a translation is done after one particular release, then the database will be out of sync with the UI. Need to find a solution to store the settings in English while showing them translated in the UI.