refactor how tasks are handled

audio tasks can now be dispatched to workers
send only task instead of taskrequest
send only task with httpdispatcher
add support for guessed user framerate

http://stackoverflow.com/questions/3199489/meaning-of-ffmpeg-output-tbc-tbn-tbr
worker handle audio tasks

add routes for video or audio task

refactor PoolConverter to handle listeners so encoding threads only have to notify one listener (the pool)
task reports now handle multiple reports and audio reports