Update get_profile.py to support reading in a profile from a file instead of from Nightscout

[scottleibrand]

As part of a data science project with @danamlewis and @azuredominique, we want to run autotune against data previously downloaded from Nightscout and stored in the OpenAPS data commons. To do so, we need to update get_profile.py with an option to support reading in a profile from a file instead of from Nightscout.

cc @viq (original author of get_profile.py via #1335)

[viq]

Same format as received from Nightscout?

[scottleibrand]

It appears so. If we can get that working, I can check if there are any discrepancies.

[azuredominique]

The dream lives on!! Thanks Scott!