add Dataset Size to Catalog

[Phileodontist]

• [x] [Integrate to API] (https://github.com/CAIDA/catalog-data/issues/547)
• [x] [Integrate to UI] (https://github.com/CAIDA/catalog-data/issues/548)

[Phileodontist]

• [x] Update data-build.py script to include dataset size

[Phileodontist]

Merge into master once the API and UI has been updated Merge request: https://github.com/CAIDA/catalog-data/pull/549

[bhuffaker]

size is now added to datsaets.