Some core gameplay features added:

- Be able to use power cores
- Be able to switch powercores by colliding with them
- Be able to drop weapons
- Shop keeper to sell weapons
- Shop keeper to sell health
- Design this (e.g. health with an 'x 5' next to it)
- Shop keeper to sell shields
- Design this (e.g. health with an 'x 5' next to it)
- Fix shop text alignment and size
Merge pull request #1 from adamjc/enemy-teleportation

Some core gameplay features added: