Downgrades the required Grails version to 2.0 and change test dependency scope

**Downgrades Grails version requirement from 2.2 to 2.0**
- Sets all test dependencies scope to test instead of compile (that is making the host app to resolve those dependencies and therefore making impossible to downgrade or upgrade the Grails version)
- Sets **legacyResolve** to false in  *BuildConfig.groovy*. Since I have upgraded the release plugin from 2.2.0 to 2.2.1, you should not have any problem. But honestly I am not sure why someone would like the legacy dependency resolution which is crap.
- All test code under the *groovy* source folder has been moved and is now under integration test source directory to prevent compilation error due to test dependencies being only available in the test scope