Changed unit tests to not use box2d.
* Added (very basic) mocks for PhysicsBody, PhysicsShapeFactory, PhysicsShape and PhysicsWorld
* Updated GameImpl.java to not always create a physics world.
* Changed the ant test target to run the all tests.
Merge branch 'development' into testNoBox2d

Conflicts:
	build.xml
Fixes to build.properties and build.xml.
* Removed an unused property from build.properties.
* Set haltonfailure to true for the junit target, or the build would pass even if the tests failed.
Changed the .classpath to use local junit .jar instead of eclipse provided one.
Fixed tests.
Revert "Changed unit tests to not use box2d."

This reverts commit b09b8355f5396867eb4a478e04c32ddc7c06547c.

Fixed Conflicts:
	build.xml
Fixed build dependency on libgdx natives.
Made the test project depend on the main project. No more F5/refresh when changing things that affects both projects.
Added a static Common class for tests to load required resources.
Modified all tests to invoke Common.loadEssentials before running.
Moved Timer and its friends to util.
Merge branch 'development' into testNoBox2d

Conflicts:
	Bullet-Inferno-test/src/se/dat255/bulletinferno/model/TimerImplTest.java
Merge pull request #3 from Jokab/testNoBox2d

Tests can now be run outside of eclipse as the box2d is correctly included in the build.xml file.
Created ResourceManager class which will be used to easily handle mappings between objects and their resources (e.g. sprites or textures).
Added ResourceIdentifier interface which all classes that want a resource associated with it need to implement.
Added more javadoc.
Added simple test case for an Enemy using the ResourceManager. Also added EnemyType to Enemy constructors so that it can be retrieved mor easily.
Fixed tests.
Added new picture for enemies to use.
Fixed bug where Enemy objects would share texture despite having different textures set.