Block categorization (#110)

* Add block categorization (is_final=)

* Add godo task for vulcanizeDB (Example of how everything could work together)

* Add unique constraint on block_number and node

* Add index on block_id for transactions_table

* Add node_id index on blocks table

* Sort transactions returned from FindBlock by tx_hash

* lowercase tx_to, tx_from like etherscan

pkg/core/block.go

@@ -12,4 +12,5 @@ type Block struct {
 	Time         int64
 	Transactions []Transaction
 	UncleHash    string
+	IsFinal      bool
 }

pkg/core/blockchain.go

@@ -4,6 +4,7 @@ import "math/big"
 
 type Blockchain interface {
 	GetBlockByNumber(blockNumber int64) Block
+	LastBlock() *big.Int
 	Node() Node
 	SubscribeToBlocks(blocks chan Block)
 	StartListening()