Merge branch 'master' of https://github.com/GL-MPRI-2014/GL_MPRI_2014 into buildings
Merge branch 'buildings' of https://github.com/GL-MPRI-2014/GL_MPRI_2014 into buildings
Added more building-related stuff

- Logics.try_next_action supports Create_unit orders
- Game engine checks that the building creating belongs to the player
- New exception when a creation order fails
- Removed Attack_building from Action