Add first of GameObjects' classes

Add GameObject class.
Add DynamicObject class.
Add Bullet class.
Add test classes for each of above.
Add test framework to project files.
Add movement tests for DynamicObject
Add Landscape class

Add destroyable flag to GameObject.
Leave some TODOs.
Add Tank class and it's derivates.
Move Direction enum to DynamicObject class.
Decorator pattern for GameObject.

Add DestroyableObject to decorate GameObjects.
Move movement implementation up to DynamicObject

Tweak tests a little to use predefined finals instead of hardcoded
numbers.
Add some tests for firing bullet
Add some tests for DynamicObject
Fix dependencies, set up tests

Tank and DynamicObject tests.
Add collision behaviour
Remove unnecessary GameObject tests
Remove unnecessary Landscape test
Cleanup a little bit
Merge branch 'feature/GameObjects' into develop