[In Progress] Scraping, Reference Ranges and Units

This is a pull request in progress. This PR includes work for practice and provider scraping (fixes #87), reference ranges (fixes #53) and units(fixes #82). I was almost done with scraping, but I decided to put more effort to scrape all the information I can find online. 

For reference ranges and units, there is more work to do. I have designed what I will be doing for units. For reference ranges, I will work on the front end and connecting reference ranges to record update values.
Ideally, yes, but these websites are so so stupid that I couldn't think of a way doing it. They start from 1 and there are some blank pages etc. in between. So they do not put providers to specific indices in a systematic way. It looks quite random.