Add docs for DNS data

[ohnorobo]

Documentation for the satellite base table and additional satellite dashboard data

View the rendered docs here:

• base table doc: https://github.com/censoredplanet/censoredplanet-analysis/blob/dns-docs/docs/base_tables.md
• outcome doc: https://github.com/censoredplanet/censoredplanet-analysis/blob/dns-docs/docs/outcome.md
• derived table doc: https://github.com/censoredplanet/censoredplanet-analysis/blob/dns-docs/docs/merged_reduced_scans_table.md