Add ability to populate missing blocks

* The command populates up to the highest known block number
 * The anticipated use case is that the listener will be running
   in parallel to the populateBlocks command
    * This will mean that the listener is responsible for picking up
      new blocks, and the populateBlocks command is reposible for
      historical blocks
 * Reformat SQL statements

pkg/fakes/blockchain.go

@@ -3,16 +3,36 @@ package fakes
 import "github.com/8thlight/vulcanizedb/pkg/core"
 
 type Blockchain struct {
-	outputBlocks  chan core.Block
+	blocks        map[int64]core.Block
+	blocksChannel chan core.Block
 	WasToldToStop bool
 }
 
-func (blockchain *Blockchain) SubscribeToBlocks(outputBlocks chan core.Block) {
-	blockchain.outputBlocks = outputBlocks
+func NewBlockchain() *Blockchain {
+	return &Blockchain{blocks: make(map[int64]core.Block)}
 }
 
-func (blockchain Blockchain) AddBlock(block core.Block) {
-	blockchain.outputBlocks <- block
+func NewBlockchainWithBlocks(blocks []core.Block) *Blockchain {
+	blockNumberToBlocks := make(map[int64]core.Block)
+	for _, block := range blocks {
+		blockNumberToBlocks[block.Number] = block
+	}
+	return &Blockchain{
+		blocks: blockNumberToBlocks,
+	}
+}
+
+func (blockchain *Blockchain) GetBlockByNumber(blockNumber int64) core.Block {
+	return blockchain.blocks[blockNumber]
+}
+
+func (blockchain *Blockchain) SubscribeToBlocks(outputBlocks chan core.Block) {
+	blockchain.blocksChannel = outputBlocks
+}
+
+func (blockchain *Blockchain) AddBlock(block core.Block) {
+	blockchain.blocks[block.Number] = block
+	blockchain.blocksChannel <- block
 }
 
 func (*Blockchain) StartListening() {}