Added onNavigated event
Added onNavigated event

Means anything can be notified when a navigation happens. Useful for
Navigation plugins where links must update after a navigation. Expected
to be lots of listeners (all hyperlinks) so it must be efficient. Use
hashed list instead of array so checking if already exists and removing
is fast.

grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation,grahammendick/navigation