Logging brooklyn-persister thread Jclouds messages in a separate file

When a server with persistence to an object store enabled manages lots of
entities the Jclouds log is overwhelmed by messages logged from the
brooklyn-persister thread (in one case logging at a rate of ~ half a
million lines every four minutes).

The appender added in this commit alleviates - a little! - this logging
overload.

Anecdotal measurements of the ratio between the persister log and jclouds
log sizes, with EmptySoftwareProcess entities:
0 entities: persister log 0.01 times size of jclouds log
1 entity: 0.36
5 entities: ~1.13
10 entities: 1.75
50 entities: 8.6
Use remotely hosted ZeroClipboard.swf

Don't include it in the repository due to licensing issues.
Fix the DynamicMultiGroup rebind actions
BindDnsServer strips invalid characters from domain names

As per RFCs 952 and 1123.
Make BUCKETS map immutable (see review comment from @aledsage)
This closes #357
This closes #283
This closes #372

* github/pr/372:
  Make BUCKETS map immutable (see review comment from @aledsage)
  Fix the DynamicMultiGroup rebind actions
Remove ZeroClipboard.swf from docs

Substitute with CDN-hosted version. Tested on a https-hosted location to
ensure correct behaviour on an environment like our live website.
Minor changes to docs build

Add #ruby line to Gemfile so that current versions of rvm detect a
known-good Ruby version and a gemset. Modify _config.yml to exclude some
source code files from the built site.
Merge and close #371
Merge and close #376
Move character set info with first 1024 bytes.

Firefox expects the header within the first 1K
Adds "None" location to arguments of start effector
Adds tests for MongoDB yaml blueprints
Fix sharded-mongodb, with CoLocatedMongoDbRouter

- was getting NPE in CoLocatedMongoDbRouter.init, while trying to
  resolve config set in yam that pointed at another entity.
EntityTestUtils: improve error messages
This closes #377
This closes #378