UI should indicate unsaved changes in the document

[csarven]

Raised by @timbl :

Maybe good to turn the background a different color or flag something in red when there are unsaved changes.

What openstreetmap does is surface a “Save” button visibly, and write in it “Save (3 minutes)” so you realize how much work you are imperiling. Or also have a timeout so that it will save if I have NOT been active for 20s say or have been active for 3 mins without saving.

[dmitrizagidulin]

Also, would it be possible to flash a notification (or some kind of feedback to the user) that a Save action was successful?

[csarven]

There is a preliminary message shown on save success re: commit https://github.com/linkeddata/dokieli/commit/02e78da01a0d30587da3b1f0ee679e059b711f53 - Needs to be prettified.