KytheInlineMetadataLoader doesn't follow rules of MappingRule

Code: [KytheInlineMetadataLoader.java](https://github.com/kythe/kythe/blob/master/kythe/java/com/google/devtools/kythe/platform/shared/KytheInlineMetadataLoader.java). The loader always creates reverse edges for GENERATES. While MappingRule says that it should be dependent on edge prefix, see comment: https://github.com/kythe/kythe/blob/master/kythe/proto/metadata.proto#L58 