Fix unit test for PathResourceLoader.

	- Files needed a renaming.
	- Simplifed tests to just test the loader, not the resource
	  manager.
Basic ZipResourceLoader unit test.
Refactor ZipResourceLoaderTest.
Add ZipResourceLoader tests for wrong use cases.

	- You can't load a file that isn't there.
	- Loading a directory should fail.
Refactor a bit bucket getter into Utils.
Clean up ZipResourceLoader.
More tests for ZipResourceLoader.