Update field in block

[Yamaguchi]

see #39

This PR is a port of the following PRs

• Remove nonce field from Block header
• Remove bits field from Block header
• Add immutable merkle root field to BlockHeader
• Add proof field to BlockHeader
• Clean up test data
• Update network magic bytes
• Remove unused parameters in chain params
• Update network magic bytes in Regtest mode
• Remove PoW functions
• Remove unused imports
• Support paradium
• Fix calculation of immutable merkle root
• Change method name maltxid -> malfix_txid

[Yamaguchi]

XFieldがまだ入っていないため、一部のテストケースをignoreにしてます。