Keep submenu open if click.

[lsaranto]

Is your feature request related to a problem? Please describe.
Currently a submenu stays open only while the mouse cursor is over the submenu. This makes it hard for people with hand coordination problems to hit the commands in the menu.

Describe the solution you'd like
The submenu stays open if the user clicks the submenu button. Moving the mouse away or over another submenu won't close the open menu.