Work toward surround sound mixing

Permit simultaneous mixing from multiple sources to 5.1 or 7.1 discrete output or saving as such in the project. This can then be mixed down to stereo, or 2.1 for CD recording yet kept in a discrete project for possible reporoduction via discrete, DTS, AC3, DD encoding as the user may now (or in the future) have the capability of producing/reproducing.