Edit board post attempt

[defnax]

No description provided.

[csoler]

Editing board posts is more complicated than it may appear:

• all versions of edited posts for a tree. Versions should be properly identified before display (unless you only want the last one) which is done e.g. in forums UI.
• everyone can post in a board. That means everyone can edit anyone's post. To prevent this, the UI needs to check that you are the right user, but more importantly, the validation in libretroshare needs to discard edited posts which doesn't respect this. This needs some engineering since the original posts may not always be accessible.
• eventually, if we copy the functionality of channels into boards, the two services will look the same, and we will not need the two of them (most probably only keep channels).

So I think we should discuss what we want to do with boards.