[messages] disable message frame sensitivity during drag

- it also disable update of new message
- it can solve a bit of #966
[messages] hide notebook and display help during drag

It is an other way to solve #966 with the advantage that the "drag
route" is made easier since during drag most of the messages window is
hidden
[messages] add tooltip to field buttons
[plotter] add a range of curves to plotter if value is an array
Merge pull request #1020 from paparazzi/messages_drag_sensitivity

Messages drag sensitivity