Add support for Micropub CRUD on contacts

[jamietanna]

WIP:

• validation for required-properties doesn't seem to be working - looks like there's nothing automagic (as I was expecting)
• commit history needs to split, as there's a mix of things being changed, here
• does it make sense to use channels in this way?
• does it make sense to have the logic for checking the post-type like so?
• remove console.logs
• don't trigger syndication

Notes:

• all the CRUD actions seem to work!

Closes #22

[jamietanna]

The test input will need to change as we've not done it quite this way