Fix maven-jar-plugin version dependency.

Force to use the maven-jar-plugin 2.4
Fix previous commit for maven-jar-plugin version

ThE previous commit put the version on the wrong place.
Push Notification Plugin - first beta release
 - directly supports 5 providers:
  - Notify My Android
  - Pushover
  - Prowl
  - LiveNotifier
  - Trendoo (SMS)
MessageEvent: removed message.type default assignment from constructor
 - reason: since getDefaultdestination() always uses the first message.type assignment,
   a call to setType() doesn't override its value (so event is sent on the wrong channel).
Push Notification Plugin - beta2 release
 - plugin now uses MessageEvent event template
 - each provider listens to its own channel
 - new feature: override global provider params with event ones, so that we can send custom one-time notification easily.
 - some code cleanup
Expose auth configuration realms on the FD APi
Market maven goal is now independent from sonatype repository. Added swagger api-docs folder to gitignore