HistoryController: setting the pageScaleFactor and scrollPoint properly

When navigating back to a page already in history

Reviewed by: Luciano Wolf
Fixing issue when going back from a page with no zoom to a page that had zoom

The page which had the zoom set, was getting its zoom reset to 1, when going
back to it

Reviewed by: Luciano Wolf
Adding API function to check whether there is a pending change in scale or position

This lets the user decides properly when to apply a scale or set
the view position, since it must only apply that when the view
has decided its final scale and position (it can be in history)

Reviewed by: Hugo Parente Lima
MiniBrowser now using NIXViewPendingScaleOrPositionChange

Reviewed by: Hugo Parente Lima