Closes #21

The who field is the user id not the name! I did this the right way
when I implemented this. Please be more careful, when you deal with
merge conflicts.

The functionality of query() is now split into query() and modify().
For all queries that modify the db (like INSERT and UPDATE) the latter
must be used. This simplifies the interface (e.g. the return value) and
later allows query caching.