[tast #68] Added support for non-standard asset directories.
[task #68] Tidied code as part of code review:

* Remove redundant tests
* Fixed code style issues
* Replaced usage of field injection with conventional constructor injection.
* Added negative tests to verify that normal projects do not link their asset folders.
[task #68] Removed code that doesn't have tests.
[task #68] Only create link if it doesn't equal default assets
directory.