[IETANKS-35] add initial board-related interfaces

Board, Tank and Projectile interfaces are the ones used by rest of game system
Merge remote-tracking branch 'origin/board' into board

Conflicts:
	ieTanks-server/src/main/java/pl/edu/agh/ietanks/game/ProjectileInterface.java
IETANKS-39: Interfaces changes
IETANKS-39: Interfaces changes
Merge branch 'board' of github.com:artekorzel/ieTanks into board

Conflicts:
	ieTanks-server/src/main/java/pl/edu/agh/ietanks/game/impl/GameBoard.java
Merge pull request #6 from artekorzel/board

IETANKS-39: Interfaces changes