Added default values for Unit::AttackResult.
Added Unit::removeFromBoard().
Reorderd tests in unittest.cpp
Reworked way Unit::attack() works.
Simplified Unit unittests.
Unit can only attack if currentMovement > 0.
Added test if Units died during attacks are removed from the board.
Bugfix: movement is zeroed correctly only for attacker.
Merge pull request #82 from namelessvoid/attack-fixes

Some fixes for new attack system.