ENH: Added mvd::ToStdString() and mvd::FromStdString(); Replaced bad conversions by safe To/FromStdString() functions.

ENH: when a receiving a mouse move event  : check if a button is pressed to detect draggin or just mouse moving

ENH: add PropagatePointUnderCursorCoordinates method implementation + signal to update the Qlabel in MainWindow

BUG: Fixing #645 and #646 - call resizeEvent() superclass implementation instead of manual call to resizeGl()

BUG: Correct handling of file path (no / should be added if path is null. Does this work on windows ?)