Canfield -> Production

- Fixed slight pause when the first bullet is fired (for real this time)
- Fixed client crash if the server player clicked the start button more than once
- Fixed crash if the server started a network game without any clients
- Mines no longer blink before they are armed: they only animate once armed
- Mines are hidden from network players, except while the mine is arming itself
- Mines no longer kill tanks in one hit, though they are still powerful
- Spawns are no longer visible, except in the TankRespawnTestApplication
- The tank now explodes on death (visually). The explosion image was adapted from spritelib.
- Tanks now respawn with full ammo & mines, and lose all trees
- Added a 1 second respawn delay
- Added more sounds. They aren't as good as the original Bolo's sounds (of course), but they are better than mute sounds, and I tried to create ones that aren't annoying:
    - mine explosion
    - pillbox hit
    - wall hit
    - tree hit
    - tank hit
    - tank explosion
- All sounds are now properly disposed when Audio.dispose is called
- 21 more unit tests

Resolves #380 & 160