Add modify button to WifiNetworkDetailsFragment.

Adds pencil icon to Wifi Detail action bar to modify the network.
Modifies package/public visibility to allow the detail package to
use the WifiDialog. Listens for changes in WifiConfigurations to
propagate changes to the UI in WifiNetworkDetailsFragment.

Changes WifiNetworkDetail preference launch to conform to pattern
of other Settings apps. Removes unused WifiDetailActionBarObserver.

Bug: 36483704, 37082355
Test: make -j40 RunSettingsRoboTests
Change-Id: Ie9dc1892eaefdfad4a6bd7040bfc5dbf6236cfb4