Use 488 code when a proposal with streams fails

Ignore-this: a7416ff2a9db8824b93660613534b413

darcs-hash:20140918140231-56b4d-5da75effc966874c66f6f11931bbb4984cca9a0e
pjsip: make H264 codec negotiation more flexible

Ignore-this: 1ffa1dcec6b5d9074192d3aa59440089

Profile needs to match in the offer and aswer, so just adjust to what the offer says. Also,
don't compare or adjust the level, since it doesn't need to be symmetric.

Reference: http://tools.ietf.org/html/rfc6184#section-8.2.2

darcs-hash:20140918155437-56b4d-093599dcc166c65fbb01dbd2dbc71afabde5b83d
Updated TODO comment in session

Ignore-this: d7af3f6765679eb69e0092c29afae44c

darcs-hash:20140918160155-56b4d-bbe126fd63ce5de183e06ed873b5d94e77f29362
Use timezone aware timestamps for Session start_time and stop_time

Ignore-this: 27768be61777241d6b51a4a123542517

darcs-hash:20140921110331-56b4d-3a855b8f34ad7b336146c763c03eed05cfb5f023
Added description for video dependencies

Ignore-this: af9226f3093d6b26e2a852bf2b24a1a4

darcs-hash:20140922012618-58252-109de0612f52389dce04d103b714fafd131f00e8
Parse and generate bandwidth info attributes (b=) on the SDP

Ignore-this: 529821201fd114f983d2c0ba79f9fa7d

darcs-hash:20140919183522-56b4d-f12e633dd29502a776193226e2b31c403c820545