Made mini map and layer list resizable.
Handle layers when moving brushes between entities.
Added buttons to layer list.
Minor changes to layer list layout.
Improved layer list toggle button images.
Improve layout issues of layer list on Windows.
Merge branch 'layers_and_groups' of z:\Documents\Code\TrenchBroom into layers_and_groups

Conflicts:
	common/src/View/wxUtils.cpp