Standalone echem "app"

[ml-evs]

A commonly requested feature is to have a standalone app for echem, where files can be uploaded without being attached to samples, and the same plotting from the block can be performed in full screen. This could then be extended to include multiple cells per plot, and might be another way of coming to a design for multi-sample blocks (e.g., as well as file upload, the full page app could support item select for cells with already attached data).

This would be especially useful now that EClab updates are causing problems for people, with the added benefit that this would support a much greater range of cycler brands. However, it would need to be made clear that this approach will never be as full-featured as eclab itself.

(cc @veronika-sedajova)