Corrected a bug preventing the suppression of a focused timebox.
Unused elements deleted or became private
Delete QAction added to suppress a timebox in smallView

Appears in Edit menu, and linked to a shortcut (Ctr + Backspace in Windows, and Cmd + Backspace in Mac)
The older way to delete has been commented for recycling.
Merge branch 'dev' of https://github.com/OSSIA/i-score into dev