[fix] fixed some quirks with plugins

includes:
  * added default values for plugin related properties (credits go to
    @dacrome)
  * loading plugin after bean initialization
  * fail deployment when `plugin.enabled` is `true` but `plugin.jar.path`
    or `plugin.classname` are not set
  * added `NoopPlugin` as default plugin
  * added properties to `src/main/deploy/addon-self-administration.properties`