Added support for passing functions back to the engine as callbacks through the LuaObject interface.

Signed-off-by: Peter Mårtensson <veritas.is.me@gmail.com>
Refactored away some completely unnecessary code in EventManager.cpp.

Signed-off-by: Peter Mårtensson <veritas.is.me@gmail.com>
Added basic support for events from lua.

Signed-off-by: Peter Mårtensson <veritas.is.me@gmail.com>