Lua: Working on Entities

Added ACCESSOR_FUNC_BOOL (creates SetX / IsX instead of SetX and GetX)
Updated: Entities now create a Lua wrapper in their constructor

Lua: Removed OnSceneNodeDeleted event
Lua: Added SceneNode/Entity :GetTable function, so information can be
stored on the entity
Lua: Added Entity:Index
Lua: Added type/tostring operator for Entity