Brooklyn node and cluster upgrade

Merges #266 (cluster upgrade) with work I've been doing on node upgrade.

Builds on #260 so please ensure that is merged first.

Needs further testing (by me at this point) but wanted to push it in case @neykov you have comments, especially on the last commit.
As commented in https://github.com/apache/incubator-brooklyn/pull/266, do we also need `addFeed(FunctionFeed.builder()...)`, or is something else controlling that the feeds be persisted?