ContentBuilder: Add method `get` to get definition or nullptr
ContentLoader: Add functionality to clone from definition specified in `parent` field in json
libentity.raycast: Add argument to specify blocks to ignore during ray casting
Chunk::rayCast: Add argument to specify blocks to ignore during ray casting.
On lua side filter blocks are passed as list of strings in form of "MOD:BLOCK_NAME"
On C++ size filter blocks are std::set of blockid_t