Add new settings to save+display multi-algo data

-New settings allow reading of the hash algorithm used to mine a particular block for coins that support this feature and have the algorithm data stored in the raw block data
-An "Algorithm" column has been added to the block page and main transaction homepage when multi-algo data is enabled
-The /ext/getlasttxs api will now return the hash algorithm if reading of the multi-algo data is enabled

models/tx.js

@@ -10,7 +10,8 @@ var TxSchema = new Schema({
   blockhash: { type: String, index: true },
   blockindex: {type: Number, default: 0, index: true},
   tx_type: { type: String, default: null },
-  op_return: { type: String, default: null }
+  op_return: { type: String, default: null },
+  algo: { type: String, default: null }
 }, {id: false});
 
 TxSchema.index({total: 1, total: -1, blockindex: 1, blockindex: -1});