Remove unused contract methods

pkg/core/blockchain.go

@@ -3,8 +3,7 @@ package core
 import "math/big"
 
 type Blockchain interface {
-	GetAttribute(contract Contract, attributeName string, blockNumber *big.Int) (interface{}, error)
-	GetAttributes(contract Contract) (ContractAttributes, error)
+	ContractDataFetcher
 	GetBlockByNumber(blockNumber int64) Block
 	GetLogs(contract Contract, startingBlockNumber *big.Int, endingBlockNumber *big.Int) ([]Log, error)
 	LastBlock() *big.Int

pkg/core/contract_attributes.go

@@ -1,20 +0,0 @@
-package core
-
-type ContractAttribute struct {
-	Name string
-	Type string
-}
-
-type ContractAttributes []ContractAttribute
-
-func (attributes ContractAttributes) Len() int {
-	return len(attributes)
-}
-
-func (attributes ContractAttributes) Swap(i, j int) {
-	attributes[i], attributes[j] = attributes[j], attributes[i]
-}
-
-func (attributes ContractAttributes) Less(i, j int) bool {
-	return attributes[i].Name < attributes[j].Name
-}