Adds extension and mime type to anchor in plates controller.
Sets format type in fluidigm_file. The login check is performed inside the
action to avoid login_required to stop the .csv conversion
Merge pull request #841 from emrojo/csv-fluidigm-file

Adds extension and mime type to anchor in plates controller.
Obserbve plate purpose
Merge pull request #842 from JamesGlover/add_plate_purpose_to_observer

Obserbve plate purpose