DBIC support

[mickeyn]

As discussed before, and following a request from @moltar, we should consider adding a DBIC support layer.

I think we need a PONAPI::Repository::DBIC consuming PONAPI::Repository and implementing the required methods in DBIC-speak.

PRs are welcome.

[moltar]

If this to go ahead, it should probably be a standalone module in order not to pull in all the DBIC deps for those who don't want/need them.

[mickeyn]

Makes sense.
We can create a plugins namespace for PONAPI and release it as a standalone distribution.