add support for ETV signaling to tsdemux
revert prior changes for 'other' stream types and re-use known_psi as suggested by maintainers
apply all requested changes for maintainer code review (see bug 708688)
remove specific PMT metadata output source pad and supporting code in lieu of PAT/PMT availability on the message bus as preferred by maintainers
apply additional requested changes after 2nd maintainer code review (see bug 708688)
Merge pull request #13 from cablelabs/ruih/signaling_support

Ruih/signaling support