extended service avout custom create/update methods, quick gui "polishing".

Fixes:
- preventing users to submit an "empty" notes
- preventing double assoc creation between tags and resource
- fixing bug in pdf-rendering-hack
- adding timestamps to all resource-actions on server-side
- removing "author"-field from resource-initialization

Features:
- introduced clickable tags in detail view to list all items tagged witht his
- modifying the filter-query on a per token base
- custom create/update methods on server-side for resources
  in preparation for possibly sanitizing html
- new tips-page and some slim editor-tips directly inline above the ck-editor
- showing username in upper nav-bar
- showing last_modified_at in detail-view
- 2 new migrations introducing edges and topics to an existing db-model

Pending:
- current layout currently does explicitly not support IE9, IE10 and Opera
- mathjax-formula preview / editing of existing needs to be fixed
- pdf-preview in editor after "OK" in selection dialog
- implementing "creator" and "contributor" edges

Testing continues.