Multi-keyword search instead of phrase search

[schwarz]

The phrase-based search implemented in the chronicle is suficient for a proof-of-concept. In practise, however, the user often wants to refine his search by specifying *multiple* sub-strings (keywords).

Of course, this changes the SQL queries a lot, but: I would not go for a complicated AND/OR search interface or even integrate regular expression search - no normal user really used such complicated stuff.

A simple AND search for multiple sub-strings is suficient!

[awagner]

fixed in r550