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

pcbnew: hooked Tool Framework into the edit panel. Added a sample selection tool (not fully functional).

Added core tool framework files + boost::context assembly stuff (initial, very buggy and unfinished work).

Now it is more verbose and the status is checked at the right moment (previously it was fine with Linux, but on Windows it showed errors).

Minor fixes. Minor code cleaning. Pcbnew: better iniatilization of members in DRAWSEGMENT, TRACK, EDGE_MOD (not bugs: just useful when using python scripting).