XD-1589 support Groovy bean definition extensions
XD-1589 changes on merge
XD-1642 Fail fast admin on startup failure

- Add `AdminPortAvailablityInitializer` to check if the admin port being used is already in use
  - Throw `AdminPortNotAvailableException` if the port is in use
- Handle any `EmbeddedServletContainerException` and exit the admin server if thrown

XD-1642 Address review comments

- Add `javadoc` for the exception classes
- Update `log` to `logger`
- Remove print stacktrace on socket close
Fine tune watch task

- Add grunt `watch` watch to listen on all the changes inside `spring-xd-ui` and
run the `build`
  - Make sure it works with `livereload` as well
XD-1507 UI: Able to submit not currently deployed jobs

* Use `ng-cloak` to minimize flicker
* Apply `cg-busy` consistently
  - Apply minimum duration of `250ms`
  - Update `cg-busy` to `4.0.2` - see also: https://github.com/cgross/angular-busy/issues/23
* Improve rendering and alignment of Growl notifications
* Color-code statuses under *Deployments* and *Executions* tab