Add scrapers style requirements to readme / templates

[josh-chamberlain]

The task:

• [ ] Represent these requirements in the scrapers readme or template as appropriate
• [ ] Represent them by creating an example scraper that meets the criteria

Good scrapers:

• Scraper must be able to pick up where it left off, i.e., not a complete grab each time, only the differences since the last run.
• Scraper saves file to our Hadoop.
• Scraper saves metadata to our database (Dolt or PostgreSQL)
• Scraper to produce a SHA256 and MD5 hash for every file it generates and record it in database. A separate script can be used for this. Workflow would be something like scraper>extractor>saver

Questions:

• Where would they save the keys? Keys or Developer API tokens, similar to those Github or other cloud services uses can be stored in config file of the individual scraper.

• Does the script have to generate its own key? We generate them on the server and assign to scrapers.

• Do all the scrapers just use a common key that is located on the scraping server? Each scraper will have its own.