NEw sub-project for simulating OSGi fragment class-loading issues

This commits adds a sub-project with a small Ant script for creating three jars - Mockito, sample source and tests. It also adds a new tests for verifying package protected mocking.

The three jars by themselves are enough to trigger the same issue which has been seen in OSGi environment with mocking package visible members. It fails if tests and sources under tests are in different jar files even though they are loaded by the same class loader.

The same tests runs fine as part of the regular Gradle build.