Added a shield animation

Collision is not handled yet.
Added new tilesets.

I added 3 new tilesets, and I experimented with remaking the level with
various tile textures. Background layer tiling causes some unexpected
visibility issues.
Small progress on health update

I managed to get player health to reduce when intersecting with enemy.
We need a delay between hits because health reduces too quickly. I tried
to use the power up animation concept, but I couldn't get the animation
to trigger. Shield collision with enemy is more accurate now.
Merge pull request #2 from Daikatana/Lakon-level-support

Lakon level support