brooklyn node and effector parameter improvements

adds a `BrooklynEntityMirror` which reflects what an entity in a remote brooklyn node is doing, and some nifty ways to test this

fixes a bug in effector parameters, was being dejsoned to `Map<String,String>`, now allows non-string parameters -- see https://github.com/ahgittin/incubator-brooklyn/commit/9ff81eaae79e14d7584a605ca41c948a9b19a45e for the fix and the unit test

also uses yaml to coerce strings to maps /cc @frontiertown - this was causing errors for people who couldn't get the json just right, yaml is much more forgiving of quotes etc (and in fact it supports key=value so the fallback strategy could be dropped!) - lots of tests for this in https://github.com/ahgittin/incubator-brooklyn/blob/96d631624eeea12dd724cc2899a17d1a062119c3/core/src/test/java/brooklyn/util/internal/TypeCoercionsTest.java

NOTE: this builds on #77 as there were merge conflicts otherwise; review and merge that PR first and this one will be much smaller (it's just the last 5 commits)