Entities

Entities are now in the game! Play around all you want. I think they're fun. They don't save yet. That's a story for the next build.

• Added boxes, slides and wheels as placeable entities. They have physics and ID.
• You can rotate them with Q and E before placing.
• Added deleter as a way to remove entities.
• Added F3 menu where you can see your coordinates and all entity ID's.
• You can no longer place walls/items inside player or other walls/items.
• Changed inventory keybind from E to I.