WebTag: set compatibility with python 2.6

* sets in 2.6 must be created using the set( iterable ) constructor
  (instead of {'a','b','c'} declaration in 2.7+)
* To provide 2.6 compatibility, creating sets with set()

Signed-off-by: Krzysztof Lis <krzysztof.lis@cern.ch>
WebTag: context function return empty string

* Changed return value of bfn_webtag_record_tags to '' from None
* If the template context function returns None, 'None' is printed
  in the template. Therefore for non-logged-users we should return ''

Signed-off-by: Krzysztof Lis <krzysztof.lis@cern.ch>
WebTag: tag editor improvements

* webtag_editor.js:
    - errors are now displayed
    - changed class name webTagEditor -> WebTagEditor
* webtag_blueprint.tokenize:
    Tags attached to the edited document can no longer appear as
    '(create new tag)' suggestions.

Signed-off-by: Krzysztof Lis <krzysztof.lis@cern.ch>
WebTag: style changes in blueprint
WebTag: removed closing X button from editor
WebTag: record association deletion test
WebTag: added signal files
WebTag: preferences
WebTag: per-module settings
WebSearch: added signal 'record viewed'
WebTag: tags in search engine
WebTag: backslash in user settings
WebTag: group tags start
deposit: added import

Conflicts:
	invenio/modules/deposit/blueprint.py