IMS: Conference URI support.

Add Telephony extras EXTRAS_IS_CONFERENCE_URI,
EXTRA_DIAL_CONFERENCE_URI which will require by Telecomm,
TeleService, Telephony, Framework, IMS framework etc.

IMS: Allow placeCall with complete uri

Add extra "org.codeaurora.extra.SKIP_SCHEMA_PARSING".
Application need to set the intent extra to dial with
complete uri.

IMS: Add participant support.

Add Phone Capabilities ADD_PARTICIPANT and
Telephony Property ADD_PARTICIPANT_KEY.

IMS: Allow add participant with normal IMS call

We should allow add participant with normal IMS
call to make it conference.
Send add participant through existing connection
of normal IMS call.

IMS: Add Participant support.

Do not create new connection while add participant
with existing call. Rather send add participant request
through IMSConference.

Change-Id: I5052710a2d11a57331bdfbe64247e6a39bf9147a