Two fixes (only one works)

- Fix crash when player dies
- Try to hide cursor (looks like a bug); opened issue in Google Code.
Resolved #13: changed my mind

- Bailed because variation doesn't look good (reduces usability: bright
colours are king)
- Created a constructor to assemble colour from RGB
Resolved #15: curved arena walls

Also fixed broken test due to fix two commits ago for null pointer when
player dies.
Resolved #17: create arena pillars

As usual, old Python code saves the day.
Resolved #12: ASCII-art title-screen (+gradiant)

- Player move component method is empty instead of null (fixes null
crash in tests)
- Screens have an abstract afterInput method, called after the player
enters any input
Resolved #16: game over screen

- Default for gui.draw is NOT to use offset
- Messages clear when changing screens
- Gui.clear() method
Resolved #31: "you die" message appears twice

- Separated out battle system update and post-update
- Show "you died" and then move on