Improve plugin architecture / Erlang release building

[wohali]

Out of trying to improve how you can ship things like full text or geo support, @davisp stated he had some good ideas around how to improve our plugin architecture. I can't find any notes anywhere, so this gets a new roadmap issue.

[wohali]

@davisp mentions:

Improved Erlang Release Building
It'd be nice to have something in the build system that allowed for custom combinations of Erlang applications to be used in the release (Erlang definition, not ASF). This would be useful for our "popular configurations" that @janl mentioned (ie, Dreyfus/Clouseau and GeoCouch being examples).

[kocolosk]

I don't think this belongs in 3.x. We closed #1516 by way of #2037, and I don't think anyone is signing up to better integrate Geospatial ahead of 3.0.

[wohali]

@davisp what do you think? I expect this was only in here for #1516 but if you had other ideas, I'd at least like to see a writeup of what you want to do before we move it out of 3.x.

[wohali]

ping @davisp for thoughts. I'm ok with moving this out of 3.x but I'd like at least a pointer to the way forward for whomever picks this up in the future.