* add bitmap accumulator
refactor vec backend so we can use it outside of tests
introduce a "hash only" vec backend for the accumulator
* get core tests passing
* initial test coverage for bitmap_accumulator
* better test coverage for bitmap accumulator and cleanup code
* refactor txhashset roots, call validate() on roots during block validation
* fix store tests
* log the "merged" root when validating roots
* cleanup, revise based on feedback
* cleanup
* rework it to pass explicit size into bitmap accumulator when applying
* introduce protocol version to deserialize and read
* thread protocol version through our reader
* cleanup
* cleanup
* streaming_reader cleanup
* Pass protocol version into BinWriter to allow for version specific serialization rules.
* rustfmt
* read and write now protocol version specific
* introduce protocol version to deserialize and read
* thread protocol version through our reader
* example protocol version access in kernel read
* fix our StreamingReader impl (WouldBlock woes)
* debug log progress of txhashset download
