Extract the bundles that Grabbit uses to an "optional" package

[jdigger]

To increase the flexibility of deploying Grabbit, the bundles that it depends on should be extracted into their own deployable package. Though Felix/AEM has some reasonably smarts when it comes to dependencies, it is also pretty inflexible in other ways. This would give a little more Operational control to people.

[jt-jayati]

@jdigger @sagarsane Is this change still needed?
cc: @jbornemann

[sagarsane]

Yes I think so.