Add all remaining prompt and popups

In reality exposing these like this would require that matching
api would be met, now there is no guarantee but this is still
internal.
Move favicon inside WebView from BrowserPage
Add activeTabChanged signal to tabmodel and load active tab when triggered.

This handles tab change from the grid and closing of active
tab.
Remove closeTab function from BrowserPage
Remove temporary properties
Remove newTabRequested property from DeclarativeTab
Remove _loadRequested from TabPage

Loading is now started immediately when active tab changes.
Remove obsoleted suspend and resume from WebView interface

suspendView and resumeView of active MozView directly.
Add WebPopupHandler for handling popups
Add WebPromptHandler for handling JavaScript alert, confirm, and prompt
Move scroll indicators to be children of WebView
Cut remaining dependencies between WebView and QmlMozView

This fixes first load not to emit activeTabChanged twice.

Currently title text blinks in toolbar when navigating links. This
is not visible in update3 version.
Wrap QmlMozView into Component
Take real tabs into use.
Fix context menu
Rename pageActive to active
Move newTabData inside TabModel
Replace titleUpdated signal with titleChanged.
Fix count to be correct once a tab gets closed.
Set contentItem (active web view) to null when last view released.