Consolidate test doubles

- Migrate various mocks of core namespaces to shared version in `fakes` pkg
- Err on the side of making test doubles less sophisticated
- Don't pull over mocks of namespaces that are only used in example code

libraries/shared/transformer_interface.go

@@ -10,7 +10,7 @@ type Transformer interface {
 	Execute() error
 }
 
-type TransformerInitializer func(db *postgres.DB, blockchain core.Blockchain) Transformer
+type TransformerInitializer func(db *postgres.DB, blockchain core.BlockChain) Transformer
 
 func HexToInt64(byteString string) int64 {
 	value := common.HexToHash(byteString)

libraries/shared/watcher.go

@@ -8,7 +8,7 @@ import (
 type Watcher struct {
 	Transformers []Transformer
 	DB           postgres.DB
-	Blockchain   core.Blockchain
+	Blockchain   core.BlockChain
 }
 
 func (watcher *Watcher) AddTransformers(us []TransformerInitializer) {

libraries/shared/watcher_test.go

@@ -23,7 +23,7 @@ func (mh *MockTransformer) Execute() error {
 	return nil
 }
 
-func fakeTransformerInitializer(db *postgres.DB, blockchain core.Blockchain) shared.Transformer {
+func fakeTransformerInitializer(db *postgres.DB, blockchain core.BlockChain) shared.Transformer {
 	return &MockTransformer{}
 }