Move artpacks to voxel-engine module

Requires deathcap/voxel-engine@fccb268d5d0d034f04f62e5eb784e5b911b96397
Update inventory-window, voxel-engine, voxel-fuel, voxel-gamemode

deathcap/inventory-window@93a0dcc91e6288aa398b5fd691fcd09e3fa726c8 Enable tooltips on first window in demo for testing
deathcap/inventory-window@c1e4aac648905e49228751873397d79e90ea7ce7 Cleanup extraneous braces in demo
deathcap/voxel-engine@fccb268d5d0d034f04f62e5eb784e5b911b96397 Load textures through artpacks module
deathcap/voxel-fuel@5ad2284e2c5ee8ae815f574facfdffe6d699c96d Add notCapable() checks
deathcap/voxel-gamemode@2bc3aa649e044427db1ae3f9519ddad41a221887 Remove trailing whitespace

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