improved tag filter (many) and support for adding tags to result-items.

Fixes:
- tags are fetched just after content submission
  (so creating duplicates of literally identical tags should not be possible anymore)
- in migration2 the score becomes a composite (not an aggregated)
- added global css class .eduzen (to not shake up the dm4-webclient)
- renamed some methods for better readability of code
- removed all "this."-calls in the current main-script
- proper rendering of submission date

Improvements:
- score-sorting is a toggle button now, time-sort is new default
- updated look & feel, revisited style definitions
- the tag-filter info dialog got slightly revised in preparation for more
- a new add-tag dialog, inlin (per item in the result-set) is functional

ToDo:
- enable editing and deletion of single resources
- allow users to manipulate the tag-filter per item
- build up a relative tag-filter (tags in relation to the remaining resultset)
- enable pasing of HTML sources into resource a field

Note: You must reset your DB.

Pending: mathjax-rendering to be fixed.