RPC: Remove all auditable data in JSONP serializer

- Remove all createdBy, createdAt, modifiedBy, modifiedAt,
  createdByUid, modifiedByUid properties from PerunBeans.
- Removed valueCreatedBy, valueCreatedAt, valueModifiedBy,
  valueModifiedAt from Attribute object.
- Keep them for Authorship since it's used for authz in GUI.
Merge pull request #198 from zlamalp/rpc

RPC: Remove all auditable data in JSONP serializer