Format sources in Kepler
Implement Status enum
Implement emitter
Use faster decoder and emitter
Fix bugs found by running test cases
Move frab[] computation to IMTF
Mark UnRLE state variables as private
Reduce memory allocation during emission
Combine prefix decoding and IMTF into one phase
Fix bug in header magic parsing
Build prefix trees in advance

This way each prefix tree is constructed only once, before any
decoding starts.  Trees for groups with the same selector are shared.
Fail on usage of invalid trees, not construction

Invalid trees are allowed to be present in bz2 streams, but they are
not allowed to be used.
Inline retriever functions to ease analysis
Convert retriever to need/take pattern
Expand block statements when possible
Move non-volatile retriever variables to member fields
Move retriever into one big switch construct
Move towards eliminating usage of InputStream