Issue #275: Add 'Show Curve Details' icon on top menu bar to show/hide control points and curve direction (dismine/valentina)

New issue 275: Add ‘Show Curve Details’ icon on top menu bar to show/hide control points and curve direction https://bitbucket.org/valentinateam/valentina/issue/275/add-show-curve-details-icon-on-top-menu

Roman Telezhinskyi:

Add ‘Show Curve Details’ icon on top menu bar to show/hide control points and curve direction

Responsible: dismi_