Big event system update

- Removed Event::mID field
- Removed Event::undo() method
- Each player now have separate scene manager
- Removed global event list
Fixed compilation error in Visualizer ctor
core/player.hpp: Added 'typedef int PlayerID'
core/unit.hpp: Added 'typedef int UnitID'
Player: Removed 'int lastSeenEventID' field and HAVE_NOT_SEEN_ANY_EVENTS macro
Replaced some 'int's -> 'PlayerID/UnitID'
core/misc.hpp: Removed unneeded (and strange) getNext(..) func
Extracted build###VertexArray() funcs from Visualizer
Visualizer: Simplified a bit build funcs
Moved vertex array builders to visualizer/meshBuilders.?pp