Whitespace trimming.
Set start/end date from selected sensor.

This is getting reset by something on the 1st click at the moment, so
that needs to be tracked down.
Merge pull request #107 from MastodonC/feature/chart-dates-from-sensor

Feature/chart dates from sensor
Whitespace tidy.
Only log in newer chrome and firefox like browsers
Merge pull request #108 from MastodonC/feature/only-log-in-chrome

Log only in modern browsers
refactor templates data handling and http apart.
Introduce a download path into the pipeline.

This will generate a csv for download in the background. users will poll
a status URL to see if it's ready.
Implement filled measurements for downloads.
wire up route with pipeline for csv download.
add some tests.

Stepping through the sequence of sequence of measurements is complicated
code. these tests do some validation on simple input data and also does
a generated test to make sure that no input breaks the code at
least. The generated test doesn't validate the output, thats for another day.
http wiring, date handling.
fix failing test.
fix data format PEBCAK.
tidy up (fix) upload to S3.
fix uris
fix s3 key for downloads.
remove redundant code.
refactor for debugging.

getting wierd error - try this to track it down.
more robust reporting after error.