Encoder

Improve the tradeoffs for the random access mode across presets M1-M13: (!2120)
Speeding up the higher quality presets by 30-40%
Improving the BD-rate by 1-4% for the faster presets
Improve the tradeoffs for the low delay mode for both screen content and non-screen content encoding modes (!2122, !2118)
Add a toggle to remove the legacy one-frame buffer at the input of the pipeline allowing the low delay mode to operate at sub-frame processing latencies
Add a new API allowing the user to specify quantization offsets for a region of interest per frame

Build, cleanup and bug fixes