Change VCM interface to take target bitrate in bits per second.

This also solves issue 1469.

TESTS=trybots
BUG=1469

Review URL: https://webrtc-codereview.appspot.com/1215004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@3681 4adac7df-926f-26a2-2b94-8c16560cd09d
12 files changed