Abandon double click

In QGraphicsScene, there is no way to differentiate single clicks from double clicks. Indeed, there is no pure “double click event”. When the user does a double click, a mousePressEvent is emitted first.

This is causing some weird behavior, when user double-clicks on the time pane for setting the cursor and the items under the mouse are selected.

A simple way to fix this issue is by allowing the positioning of the cursor only when clicking on the timescale.