addresses review comments, cleans up quite a few things.  most importantly:

    * change start sequence so that:
      * HA is known when the web console comes up (initPersistence before startWebApps)
      * launcher exits if persistence is misconfigured or if it fails to rebind

    * big tidy up of startup logging around persistence/HA
    * fix how jclouds integration tests inherit (couldn't find a nice way with any combo of @BeforeGroup / @BeforeMethod, so have just repeated all the test methods from supers)
    * support brooklyn.persistence.location.spec being set in brooklyn.properties
    * support brooklyn.persistence.backup.required (note, this defaults to false in obj store, but we seem to be pretty good about not clobbering things; even so, some prod usage may want versioning on the obj store)
    * clean up how persistence store initialization (prepare) is done
    * refactor of how object store items are written, with wrapper which handles locking, cutting code and fixing append for file and jclouds obj store