Rich text support - editor & display

[pinkforest]

Currently it's all rendered as ascii and it can get pretty messy

Many authorities are using rich text and people can use bold for headings etc. to make requests more readable.

This would also help displaying responses in more as it was intended by the sender

[benrfairless]

I need to search upstream (https://github.com/mysociety/alaveteli) however if I remember correctly there is a reason why upstream chose not to implement this.