[FR] Move cards between boards

So, this is a request mentioned here: #16

First of all, thank you for implementing some of the other requests (colors and tags).

I don't know how Joplin handles notes in kanban boards, but having the ability to move notes between boards could be useful - I'm trying to unify some kanban boards and this could come in handy.

I know one could just copy and paste the note contents from one note to another, but when there are many notes the chance of making a mistake increase. If it is worth the fuss I understand.

Start by reviewing the related request in issue #16 and the existing board and note-handling flow. Done should mean notes can be moved between boards reliably, without requiring manual copy and paste.

Written by the indexing model from the issue text.