templates/upload/details: pass baro variable to bindTimeFields

... which was missing before...
lib.datetime: add to_seconds_of_day function
views.upload: add takeoff/landing times as seconds to flight trace dict
upload.js: pass real takeoff/landing times to initBaro
model.flight: add release_time and end_time columns

Both mark the begin and end of the scoring window.
views.upload: add real release and end time to trace dict
lib.xcsoar.analysis: store takeoff_time as release_time...

and landing_time as end_time, until we have a better solution...
views.upload: split update method

Prepare updating single flight per ajax request
templates/upload/details: add names and ids to input fields