[dmd-internals] Trello permissions

[Alex]

Hi,

The Trello org is currently private (i.e. completely sealed off to
non-members). I think we should fix this.

I'm thinking that it's a good idea to

* make all boards publicly viewable;
* make anyone able to vote and comment on cards;
* make org members able to add others and themselves to boards;
* restrict card creation to org/board members.

Thoughts?

Regards,
Alex