* Added sizeshift to proof of work and encoding as VLQ
* Fix some loose ends to get things to compile
* Rename sizehift to min_sizeshift
* Pipeline checks for PoW Cuckoo Cycle size shift and adjustment
factor before difficulty comparison.
* Working delta+VLQ encoding of u64 PoW, unfortunately still a
little larger than u32, at least for Cuckoo30.
* Changed binary encoding of proof of work to a sequence of exact
compact bit representation of each nonce. Somewhat simpler,
shorter and matches the data to be hashed.
* Few fixes based on @tromp feedback:
* Max nonce is 2^(N-1)
* Need a separate constant for reference sizeshift
* Cuckoo implementation now conserves sizeshift. Test providing a
block at higher sizeshift.
* Last small overflow protection
* we do not need Merkle proofs to spend coinbase outputs
we only need the output_mmr_size from the block header
* tests working with no Merkle proofs in inputs
* First pass at restructuring the keychain crate and introducing a Keychain trait
* Parameterized everything that had to. Stuff compiles.
* More stuff compiles, fix most tests
* Big merge, pushing down opening the keychain forced adding factory methods on trait
* Test fixes for pool and servers crate
