Editor contact autocomplete performance & refine stream filter and forum notification behaviour (mostly for performance)

Editor contact autocomplete performance:

This slightly changes the editor contact autocomplete behaviour.

Queries using like with a prepended % to the query string do not make use of indices. This is no big issue when we query abook but can get really slow when xchan table is involved.

This commit changes the xchan table only queries to use the str% format. This means that the result set for channels we are not connected with will change in a way that xchan_name and xchan_addr will be matched only from the beginning of the name or address.

This commit also changes textcomplete to only start the query after the 3rd character. the result set between 2 and 3 characters is mostly very different and only from 3 chars on there is a high possibility the channel we look for is already in the result.

Refine stream filter and forum notification behaviour (mostly for performance):

Personal posts will be displayed in unthreaded mode and clicking a forum notification will show only the unseen items of the forum in unthreaded mode. Group the filters in the widget - threaded at the top, unthreaded beneath.