Add activation delay

Add new option "activationDelay".

This option adds a delay (in milliseconds) before really opening
submenu to prevent flickering submenus when moving cursor quickly
between rows.

If this option is not set, no delay is applied.
Update documentation for "activationDelay" option
Add parameters to activate & deactivate functions

Activate : add previously activated row as a second parameter if any.

Deactivate : add next activated row as a second parameter if any.