eduZEN adaptations to run on deepamehtas latest 'neo4j 1.2' and minor fixes.

adaptations:
- removing the consumed- and the providingServiceInterface-Property
- override new (inherited) serviceListeners

fixes in the ui:
- clearer error message in case of a failed login, better pre-set help-link contents
- added a link on our front page to the first introduction for users
- fixed "MatJax" preview field in approach and comment-view
- got rid of the "host"-setting from all client-side scripts (using "/" instead)

Note:
Migrations need to be updated, if this eduZEN will be re-installed by someone ("Whole Topic Type" > "Whole Type")
https://github.com/jri/deepamehta/commit/a0aea34fac1397097483d66857011d42878c18f1