As discussed in #12, here is my take on start and due date functionality for Wekan.

I updated the original pull request a little bit, but these points are still valid:

• Hook into the wekan activities / notifications feed. A reminder message e.g. 2 days before an assigned card expires would be awesome..
• Make the moment locale change reactively, so the date format changes when the user selects a new language.

Also, i would suggest putting the badges before the members in the minicards, but since that's more of an aesthetic opinion, i did not include it in this pull request.

Some more thinks to consider:

• I now used the atmosphere version of bootstrap-datepicker. I would have preferred to use the npm package, because atmosphere only has an outdated version available. But since Wekan is not really set up in a npm / ES2015 kind of way, the atmosphere package was the easiest solution and it gets the job done.
• mquandalle:moment is stuck at v2.9.0 of the moment.js library, which does not support calendar time formating. Fortunately it degrades gracefully, so it will just start working, once a newer moment.js is used. It might be a good idea to use a different moment wrapper, like this one. That would require a small rewrite of how dates are currently displayed, though.

Additionally, as @xet7 pointed out, it would be nice to be able to import due dates from Trello.

If you're ready to merge, i can squash it done into a single commit, if you prefer it that way.