Default tool: Skip first move event to avoid accidental move during mouse button press

Summary:
It is very easy to accidentally move a shape if one has a sensitive mouse.
This just swallows the first move event which is likely to be small anyway.

Reviewers: boemann

Reviewed By: boemann

Tags: KEXI, #calligra:_3.0

Differential Revision: https://phabricator.kde.org/D4266