[IMP] New TextIndex using Whoosh
[FIX] Adapt category and conference search

- Closes #1381
[FIX] Small refactor WhooshIndex class

- See #1381
[MIN] Moved commit
[VER] Recovered changes lost in rebase
[MIN] added itervalues to ObjectHolder
[FIX] Variable missing in search event
[FIX] Missing code for indexing in whoosh
[FIX] Using decode to index unicode values
[MIN] Set right version of whoosh