Add section on removing message from holding pen.

Text adapted from https://github.com/mysociety/alaveteli/issues/465
Add a section on editing outgoing messages

Text adapted from https://github.com/mysociety/alaveteli/issues/465
Add a section on banning a user.

Text adapted from https://github.com/mysociety/alaveteli/issues/465
Add a section on deleting requests.