[fix] removed unique constraint

until we know how jpa merge changes and in which order
Merge pull request #138 from dacrome/performance

[task] performance
Merge pull request #137 from davidmoebius/cleanup

[cleanup] and adding license header
[task] move extension update code in distinct ExtensionUpdater class
[task] extended ExtensionUpdater to support delete
[fix] change from MultiValueAttribute to Email type
[fix] now getting right exception if filter field not available
[task] refactor update Extension and adding some unit tests
[refator] deletion of activation token changed to scim standard
[cleanup] removed unused method
[refactor] test changed to fit new behavior
[fix] extensionField will only be tested to null if it was created
[task] adapted registration module to fit new extension update behavior