rm propagation stoppers
rm redundant test for active menu
Expand test of focus movement
retab
change condition test on next()
Bugfix: Mouse enter to another menu flickers

The bug was that if you opened a menu, and then
you entered into another menuItem the new opened
menu would close.  It created an odd flicker
effect.
Clarify menuItem mouse behavior handler

1.  rename to
`_mouseBehaviorForMenuItemWithSubmenu`.  This is
more accurate
1.  Wrap a complex boolean test into an intention
clarifying variable name
remove unneeded event handlers
annotate complex conditions test