feat: added hemi btc block rpc calls

[ClaytonNorthey92]

added two new endpoints:

• hemi_getBtcBlockByHash
• hemi_getBtcBlockHeaderByHash

added tests

fixes #68

examples:

curl http://localhost:18546   -X POST   -H "Content-Type: application/json"   --data '{"id": 1, "jsonrpc": "2.0", "method": "hemi_getBtcBlockByHash", "params": ["0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206"]}'

{"jsonrpc":"2.0","id":1,"result":{"Header":{"Version":1,"PrevBlock":"0000000000000000000000000000000000000000000000000000000000000000","MerkleRoot":"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b","Timestamp":"2011-02-02T23:16:42Z","Bits":545259519,"Nonce":2},"Transactions":[{"Version":1,"TxIn":[{"PreviousOutPoint":{"Hash":"0000000000000000000000000000000000000000000000000000000000000000","Index":4294967295},"SignatureScript":"BP//AB0BBEVUaGUgVGltZXMgMDMvSmFuLzIwMDkgQ2hhbmNlbGxvciBvbiBicmluayBvZiBzZWNvbmQgYmFpbG91dCBmb3IgYmFua3M=","Witness":null,"Sequence":4294967295}],"TxOut":[{"Value":5000000000,"PkScript":"QQRniv2w/lVIJxln8aZxMLcQXNaoKOA5CaZ5YuDqH2Hetkn2vD9M7zjE81UE5R7BEt5cOE33uguNV4pMcCtr8R1frA=="}],"LockTime":0}]}}

curl http://localhost:18546   -X POST   -H "Content-Type: application/json"   --data '{"id": 1, "jsonrpc": "2.0", "method": "hemi_getBtcBlockHeaderByHash", "params": ["0f9188f13cb7b2c71f2a335e3a4fc328bf5beb436012afca590b1a11466e2206"]}'

{"jsonrpc":"2.0","id":1,"result":{"Version":1,"PrevBlock":"0000000000000000000000000000000000000000000000000000000000000000","MerkleRoot":"4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b","Timestamp":"2011-02-02T23:16:42Z","Bits":545259519,"Nonce":2}}