Allow use by Diasend users that don't have NightScout

[tim2000s]

Currently, in order to use autotuneweb, it's necessary to be able to pull data from NightScout for it to run.

Many non-looping users store pump and CGM data in Diasend, and would be potentially better served by being able to simply upload data to autotuneweb from Diasend. There are currently tools available to upload a Diasend .csv file to NightScout. Potentially these could be repurposed for use with autotuneweb to allow the same file to be uploaded and run through the functionality here.

NightscoutLoader: https://github.com/gh-davidr/NightscoutLoader

Equivalent enhancement request for NightScoutLoader: https://github.com/gh-davidr/NightscoutLoader/issues/12#issue-458184361

[MarkMpn]

AutotuneWeb is simply a wrapper that ultimately invokes the standard oref0 autotune command line, so while I'm sure it would be possible to allow a file upload into AutotuneWeb, there would need to be a corresponding command line option in the core autotune script to make use of the file, as I believe the only option at that level at the moment is to supply the Nightscout URL.

If an option is added to the autotune script to take its data from an input file rather than a URL I'm sure I could make the appropriate changes to expose that functionality in AutotuneWeb.