Add GeneralNodeDatumMetadata entity and DAO API.
Implement Ibatis implementation of GeneralNodeDatumMetadataDao.
When metadata changes, ensure cached JSON string removed.
Add helper constructor.
Add support for adding and querying GeneralDatumMetadata in DataCollectorBiz. This will support nodes uploading new metadata.
Support property info metadta merge.
Add DatumMetadataBiz and expose methods via endpoints in /solaruser API for adding/querying general datum metadata.