Emit also selected name of selected element to Object Editor
svg-drag: rename tr to objTransform
create object for draggedObject (WIP)

THis is completely messy, and I have only to commit it because I have
to leave the computer.
make svg->getRoundDiffPos more generic
svg: Improve Point().distanceTo

Now this method uses getRoundDiffPos, so it should be obsolete
to call this at any other place.

Maybe getRoundDiffPos should now be integrated into the Point class?