Tuesday & Wednesday work (#30)

* Fixes an incorrect link in dashboard

* Disables the symposion sponsors app

* Adds redirect links for login/logout; adds THEME_CONTACT_EMAIL value

* Re-adds colophon/copyright message.

* Adds AceMarkdownEditor widget

* Tidies up the generated HTML

* Tidies up form snippet behaviour

* Proposals forms now use the markdown editor

* Monkey patches the markdown editor into the speaker form.

* Adds missing field to proposal details

* Fixes #10 — adds a link to random unreviewed proposals

* Minor tweaks