Add bucket to be part of object struct, reply back with BucketNotFound

for erroneous Object Put requests.

Other minor cleanups, to follow

  - https://github.com/golang/go/wiki/CodeReviewComments

pkg/storage/storage_errors.go

@@ -10,16 +10,16 @@ type ObjectExists struct {
 	Key    string
 }
 
-type BucketNameInvalid struct {
-	Bucket string
-}
-
-type BucketExists struct {
-	Bucket string
-}
-
 type ObjectNotFound GenericError
 
+type GenericBucketError struct {
+	Bucket string
+}
+
+type BucketNameInvalid GenericBucketError
+type BucketExists GenericBucketError
+type BucketNotFound GenericBucketError
+
 func (self ObjectNotFound) Error() string {
 	return "Object not Found: " + self.Bucket + "#" + self.Path
 }
@@ -35,3 +35,7 @@ func (self BucketNameInvalid) Error() string {
 func (self BucketExists) Error() string {
 	return "Bucket exists: " + self.Bucket
 }
+
+func (self BucketNotFound) Error() string {
+	return "Bucket not Found: " + self.Bucket
+}