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.
Should probably access `publishedValues.isEmpty` while synchronized.
But you'll probably get away without, given it is piggie-backing on the "happens-before" of the `semaphore.tryAcquire`, so no strong feelings.