save message tags patched the issue with nonexistent grouptagvalue

Repaired crash, when saving the masage tags to eventfiltertagvalue, if
the grouptagvalue does not exist. Only temporarely though!
save message tags catching exception

Repaired crash, when saving the masage tags to eventfiltertagvalue, if
the grouptagvalue does not exist. Only temporarely though!
Filter tag value frontend. With debug code included

This comit includes first "working" preview of events sorted by tags. It
is not functionall, and it includes tones of obsolete code.
Filter tag value frontend. Added links to the list

created links to the list of events wit the same tags.