Use tear-off menus (and remove toolbars)

[andrea-bistacchi]

Toolbars can be removed in the project wndow and in other views if we activate the tear-off property of all menus.

Details here in the QMenu Class documentation.

[mcbaguetti]

I close this issue with this commit: https://github.com/andrea-bistacchi/PZero/commit/81587740b73d8f80ae55b8f0ce2f07a24da30962. The last commit removed the duplicated toolbars and added the possibility to tear-off all the menus on the menuBar

[andrea-bistacchi]

Very good!