Mcresources

Updated for pack format 6 / 1.16.2

- Fixed wall block state and models
- Added initial concept of world generation builders

Fixed two issues with the resources generated by `make_door` and `make_button`

[This was an automatic build]
// todo: add changelog

Minor improvements
- `ResourceLocation` handling was re-done internally, which should function the same but be more consistent when handling namespaced or not resources.
- Added a section to the `README` detailing the block loot table functionality.
- Added an optional `loader` parameter to both block and item models, for use with forge custom model loaders.
- Added an `ingredient` function to `mcresources.utils` that matches minecraft's `Ingredient` better than `item_stack`

More factory methods have been added to `BlockContext` for various standard block states. These include:
- `make_wall()`
- `make_door()`
- `make_trapdoor()`
- `make_button()`
- `make_pressure_plate()`

The `LootTables` class was removed - it's functions are now importable directly from `loot_tables` instead.

A number of bugfixes (mostly to do with the block state factory methods):
- Fixed `stairs` using the wrong models.
- Fixed incorrect `True` keys in blockstates (bad find-replace)
- Fixed fences inventory models not generating correctly.
- Fixed block and item tags using `with_tag`.
- Fixed `recipe` not properly expanding conditions.

Added a couple factory methods to create common sets of blockstates and models. These include `make_slab`, `make_stairs`, `make_fence`, and `make_fence_gate`, with more planned.

Internally, refactored `ResourceLocation` handling - it should be *much* more consistent with how it handles and identifies identifiers of different domains from the root `ResourceManager`s domain. This is most prevalent when using tags and either trying to specify external blocks, or external tags with internal blocks.