Handle new device data in POST /v1/account/login

[philbooth]

curl -v \
-X POST \
-H "Host: api-accounts.dev.lcip.org" \
-H "Content-Type: application/json" \
-H 'Authorization: Hawk id="d4c5b1e3f5791ef83896c27519979b93a45e6d0da34c7509c5632ac35b28b48d", ts="1373391043", nonce="ohQjqb", hash="vBODPWhDhiRWM4tmI9qp+np+3aoqEFzdGuGk0h7bh9w=", mac="LAnpP3P2PXelC6hUoUaHP72nCqY5Iibaa3eeiGBqIIU="' \
https://api-accounts.dev.lcip.org/v1/account/device \
-d '{
  "name": "My Phone",
  "type": "mobile",
  "callback": "https://updates.push.services.mozilla.com/update/abcdef01234567890abcdefabcdef01234567890abcdef",
  "publicKey": "468601214f60f4828b6cd5d51d9d99d212e7c73657978955f0f5a5b7e2fa1370"
}'