- Central widget no longer stacked. Views are added/removed to layout
to switch view
- Dock Widgets are globals with single instance of each type
- Both central views and dock widgets are just-in-time created saving
lots of memory

Renamed some variables.
Removed unused joystick settings stuff.
Deleted unused actions.

This way OS X correctly positioned menu items

No major functionality changes.

Tried to order items in order of importance.
Also all perspectives now have their own shortcuts.

Both on the backend (replaced with DEFAULT view) and on the front end (removing UI menu items).

There were two separate actions for the simulation view, leading to
strange behaviour when it was selected.

Signed-off-by: Koen Kooi <koen@dominion.thruhere.net>

Reworked the styling UI. Now there are 4 options: light, dark, custom_light, and custom_dark. Things don't quite work right, but the proof-of-concept is done.

Changes for the new "View" navigation, and fixes to get most of the dockwidgets working with the new view system