Huge updates to Bullet Selection!

* Added bullet belt and reserve slot tags.
*Added tons of textures and materials for various UI elements.
*Created 'BulletBelt' object and components for managing the UI for the
bullets on the belt.
* Created a 'BulletReserve' object and components for managing the pool
of bullets that can be dragged into the belt.
* Created a 'main' scene and input component for handling the bullet
assigning.
* Tons of other random things! Hope this works!