Fix assert in the calligraphy tool when painting

There were two problems:

1. KarbonCalligraphicPoint returned the paint information by-value, which meaned that the distance was registered *not* on the real pi object, but on a temporary copy of it. Obviously enough, it asserted when the temporary was destroyed right after the the registrar registered the distance information on it.

2. registerPaintedDab() should be called _after_ the dab was painted, right what its name says: "painted", not "to be painted".