work with spec-stats

[fippo]

we're mostly relying on the google stats, we should be working with spec-stats more. One day...

[henbos]

Today is a (one) day

[fippo]

patches welcome? 😄

[fippo]

Quickly glancing over the individual feature files:

• features-client is not using getStats
• features-connection largely uses spec-stats since we mangle them a bit. Exceptions are VideoBwe, dtlsCipherSuite, srtpCipherSuite. Its a bit unclear if candidate-pair in spec-stats has selected but the spec-way to get the currently active candidate pair is a bit different.
• lots of the features-stream stats use goog values. Also spec-stats have a different way of calculating rates.