TX Loader

### Features: - Provides a directory which acts as any other resource pack - Provides a directory which overrides all other assets with the same resource locations - Official assets can be downloaded automatically at startup from the official Mojang servers (Mojang's [Brand and Asset Guidelines](https://www.minecraft.net/en-us/terms#terms-brand_guidelines) are not violated this way). Pack devs can do this via a JSON config, mod devs can use a builder via `glowredman.txloader.TXLoaderCore#getAssetBuilder`