1. rewrite of the Haven variation of the Pricing Record class to support:
- versioning of the PR format
- nested supply_data and asset_data structs
- verification of the signature using a variable-length string (not R+S)
2. calculation of the slippage tallies for a block in add_block(), so that
we can work out the yield that is due to be paid out for the block.
Loads of little fixes and cleanups.
Lots of refactoring still to be done in the codebase, and currently TRANSFER
method does not work - the daemon does not send the real output for some reason.
Lots still to do - please be patient.
This code is NOT ready for use. Or testing. Or anything else.