This commit addresses Issue #27. Made additional changes as well...

* I believe I've finished working on all Unit Tests
* I've updated the 'PhpRbac/tests/README.md' file to reflect the changes made
* I've removed all of the v1.0 core Unit Tests (was located in the 'PhpRbac/src/PhpRbac/core/tests/' directory)
* I've removed the 'PhpRbac/src/PhpRbac/core/sql/' directory and made all necessary adjustments. Everything now points to the 'PhpRbac/database/' directory
* I've created the 'PhpRbac/src/PhpRbac/core/README.md' file to briefly explain the existence of the 'PhpRbac/src/PhpRbac/core/' directory