Regular expressions in C2 are partial matches per default

[Akron]

First fix #66!

The C2 regular expression #REG(bal.?m) is currently translated to the Lucene equivalent bal.?m/ in KorAP. While C2 interprets regular expressions as partial matches, Lucene interprets them as full matches. So the valid interpretation of the first query has to be /.*bal.?.*/ instead. To have a full match, C2 requires anchor operators, i.e. #REG(^bal.?m$).