refactor PhysicsContact inherits from EventCustom; simplify emitting collision events
fix compile error
remove the workaround cast
Merge branch 'physics_event' of https://github.com/edwardzhou/cocos2d-x into iss3716_refactor_physicscontact

Conflicts:
	cocos/physics/CCPhysicsContact.h
issue #3716: refactor physics contact
closed #3716: edit lua support
Merge branch 'develop' of https://github.com/cocos2d/cocos2d-x into iss3716_refactor_physicscontact
Added getPropertiesForGID that assings value instead of returning it.
fix string size check and assert condition

1. std::string::size() return size_t (is never < 0)
2. "event must be larger than 0" and 'event' has unsigned int type
Testing a new TMX renderer

faster
sort of working
what is happening here?
working!!
code cleanup
isometric kind of working
iso almost working 100% ok
iso almost working
Code is cleaner
More fixes and "tiles" is an uint32 (GID)
more cleanup in TMX code