Removed unused H2 priority related code. To be moved to client

[ok2c]

No description provided.

[ok2c]

@arturobernalg Okay. here's the latest

1. I removed unused protocol code
2. I completely re-wrote PriorityFormatter for memory efficiency. Please take a look at my implementation and yours and compare them in terms of intermediate garbage generation. Message parsing / formatting usually used are in the hot execution path and MUST be efficient. That also implies memory efficiency.
3. Changed the sample application. Classic over Async is still experimental and will likely be experimental for a long time. we should not promote it unless InputStream / OutputStream compatibility is really a necessity.

[arturobernalg]

LGTM. @ok2c I never attached to H2Processors because was a experimental feature.