Apply API review to android.net.Network:

- socketFactory() renamed to getSocketFactory()
- Make sure bindProcess() documentation points developers to getSocketFactory() as the preferred approach
- Move bindProcess() and unbindProcess() to ConnectivityManager.setProcessBoundNetwork() -- passing null clears it.
- Move getProcessBoundNetwork() to ConnectivityManager.getProcessBoundNetwork().

Bug:15142362
Bug:13885501

Change-Id: Ia55c59d52e1ec8bf10dd0d9d037bd04c0998bc71
(cherry picked from commit 5ca1e6675bf4182b6e9ca76a7696bf2e38e96c4f)