Bug fixes for command, achievements and tests added

Most things are small. Some comments on the tests are needed whether I need to test more in them.
It should be noted the achievement tests are only testing the achievements and not the observer pattern.

Bugs Fixed:
- Deleting player in Command destructor
- move changed to moveDirection enemy

Changes:
- Added unlocked achievements list to achievement system
- fixed destructor of achievement system

Tests:
- Added test for command: test single key, key sequence
- Fixed tests for achievements