* [chain]
- Add basic chain cfg parameters
- Added logic to insert genesis block, if it is a fresh database
- changed SaveBlock to ProcessBlock
- changed SaveHeaders to ProcessHeaders
- Changed parameter from a wire message to the payload, for header and
block processing
- Added check in chain for when the block is in the future, i.e. not at
the tip of the chain
- Added custom error returns, to distinguish between a database error
and a validation error
