This is a exception to be thrown when the error occures because
of bad user data. We don't want to print a full stack trace in
these cases but just tell the user what went wrong.
The new functions always creates normal and partitioned functions.
Also adds specialised connection and cursor classes for adding
frequently used helper functions.
Given that only one command will be executed in the end, it is
not necessary to import what amounts to the whole library. This
becomes in particular important for update functions that have
a dependency on pyosmium. The dependency can remain optional for
people not using updates.
