Add skeleton for map saving/loading
Simple map loading passes
At least 2 layer loading works
Remove <cassert> include from TileMap.cpp
Clean up a bit
Format with astyle
Make drawGridForLayer parameter unsigned

Rationale:

The value would be converted into an unsigned value anyway when comparing,
and this avoids warnings.
Editor/LayerTab: Fix segfaults

Have code that manipulates the TileMap's layers use the size of the
actual TileMap instead of the layer tab's size.
Editor/LayerTab: Remove private data member 'layers' to 'layerWidgets'
Editor/LayerTab: Add layer to map first, update layer tab after
Small whitespace fix
Remove unused method
Some reordering
Whitespace
Make layer name a property of Layer instead of LayerWidget
Fix crash
Fix a bug with loading
Fix crash when adding a layer
Make Layer's trivial functions inline
Rename and prefix private members of Layer with m_