Refer to bug URL in PgmResourceBundle
Change p2 stats URL to avoid extra redirect response
Extend PgmResourceBundlePDETest

Ensure that calling initialize() twice on the same thread does not do
any harm.
Implement minmal 'cr' command to change the current repository

The SkeletonPDETest now holds a new test that executes a 'cr' command
and verifies that the success-message is written. The RepositoryProvider
was extended to create two repositories and also hold a current repository
that can be get and set.

Related issue: #4
Patch classes in org.eclipse.jgit.pgm

Replace classes Die and TextBuiltin with versions from the current
development stream.

Related issue: #16