collect packet rate stats in NodeList
add some basic stat collection to avatar-mixer
add trailing sleep and performance throttling logic to AvatarMixer
suppress trailing sleep ratio debug
at minimum send packet rate stats for ThreadedAssignment subclasses
pretty up the stats table
use explicit float casts where appropriate
make stats red when they become stale
use the performance tuning ratio in avatar mixer to send less
cast numerator to float before divide
Merge pull request #2472 from birarda/domain-json-stats

add minimal packet rate stats to all nodes, a little extra to avatar-mixer
Merge branch 'master' of https://github.com/highfidelity/hifi