Added a private apis jar that includes explicitly supported APIs that are not useful for 3rd party developers.

The first set of these APIs is for telephony:

Added some APIs to ITelephony and created a first party framework for them

toggleHold()
merge()
mute(boolean mute)
playDtmfTone(char digit, boolean timedShortCode)
stopDtmfTone()
swap()
addListener(ITelephonyListener listener)
removeListener(ITelephonyListener listener)

Bug: 13302451
Change-Id: Iefec5688c26a1b4fe77f5643eba6e1690a057ee6