PCB items are refreshed on GAL switching (changes made using default renderer are displayed by GAL).

Added const to GetColor() and GetType() functions in WS_DRAW_ITEM.

Changed focus owner of LayerWidget to EDA_DRAW_PANEL_GAL to make keyboard events work (apparently everything works fine, to be tested more extensively).
Removed unnecessary event hook from EDA_DRAW_PANEL_GAL.

Smarter selection algorithm (does not allow to select both whole MODULE and its parts at the same time).
Cancel event works better (selection box does not appear after cancelling the selection tool).
Removed blinking selection box effect.
Model is accessed in more appropriate way (getModel() method).

Changed reaction of SELECTION_TOOL to ToolCancel event (first event clears selection, second one deactivates the tool).

Moved VIEW_ITEM::ViewGetRequiredLayers() functionality to the VIEW class. Now required layers are set per layer basis instead of per item.