Proposal to add packaging to mockito-testng with gradle

This pull request was done while the Hackergarten event at devoxxFR.

This is a packaging proposal for mockito-testng module with gradle.

* 'grade build' create a 'mockito-testng-1.0.jar' and 'mockito-testng-1.0-sources.jar' in ROOT/subprojects/testng/build
* 'gradle uploadArchives' package mockito-testng as maven artifact (local repository in ROOT/target/maven/repository for now)

I've also loaded version.properties in gradles files (and deleted reltated TODO) to re-euse version number, and added mockito.testng.version in this file

I think it will need to be adapted to your build needs (build path(s) for example), but it provide a start.
It also currently miss the osgi repackaging.