Frontend team - Githubissues

Change Documentation to markdown viewed from repo / Export sensor data on delete sensor

Change all documentation to be viewed in github in markdown format.
Add an attribute to the settings.py file: GITHUB_DOCS_ROOT, which points to the root of all of the docs in the github repo.

Other:

Remove direct link to Grafana from GFConfig. Users were finding it confusing to have that extra link there.
Export particular sensor data on delete sensor. Allows the user to export data for a sensor prior to deleting the sensor.

Put an x in the boxes that apply

[ ] Feature (non-breaking change which adds functionality)
[x] Bug Fix (non-breaking change that fixes an issue)
[ ] Breaking Change (feature/fix that causes existing features to not work as expected)
[x] Documentation

[n/a] I have read the [contribute]contributing doc
[x] Classes, scripts, and environment variables follow existing naming convention
[x] Lint and Unit tests pass locally
[x] New features on hardware have been tested on a local Raspberry Pi
[x] Mention new programs/binaries if any must be installed along with this change
[x] Mention new environment variables if any have been added to hardware/env file
[x] Test coverage should not drop more than 3%
[x] Any new required python modules are added to the requirements.txt