Upload should only run, when measurements are not running

[dostuffthatmatters]

Reason: computer should not get too hot and slow.

Solution: Binding the should_upload_abort callback to the measurements_should_be_running state and don't even start a new upload when this is the case. This way we don't have to configure any times for the upload to run.

Config addition: Add a config parameter allow_uploads_during_measurements and explain this button in the UI. Set this to false in the migration.