Convert [Contact:<id>] into render(Contact.find(<id>)) in govspeak
Display [Contact:<id>] info in admin

1. On the list of contacts, show the markdown to use for that contact
2. Mention it in the govspeak helper sidebar when editing content
Use govspeak_to_html instead of wrapped_xxx(bare_xxx)
Allow for extracting the embedded contacts from a chunk of govspeak
Show a warning if a press release doesn't have any embedded contact info
Add new Corp Info Page type for Media Enquiries

The intention is that they will write something in here and embed all their contacts for media enquiries.
Cope with nil govspeak when dealing with [Contact:<id>] constructs
Merge pull request #441 from alphagov/media-contacts

Tracker: https://www.pivotaltracker.com/story/show/32825461

Allow embedding of contact information in govspeak using [Contact:<id>]. Orgs now also have a new corp info page called "Media Enquiries" and they can use this to embed all the contacts that are for media. Finally, we display a warning for press releases that do not have any embedded contacts.