AGSEC-63 - Refactor AeroGear Security and Update to PicketLink beta4

Good morning, some changes attached into this PR:

- AG Sec PicketLink was updated to beta6 and of course the API backward compatibility was broken and fixed
- This PR was released under snapshots on Nexus, so if you want to try add at your pom.xml:

      <dependency>
            <groupId>org.picketlink</groupId>
            <artifactId>picketlink-api</artifactId>
            <scope>compile</scope>
            <version>1.2.0-SNAPSHOT</version>
     </dependency>

And of course, make sure that all the snapshot repositories are properly configured.