{{ doc_info|pretty_doc_info }}

Introducing a new template filter called `pretty_doc_info`, and it's code counterparts `get_doc_info` and `get_doc_info_by_id`. These are used to solve the problem of having just an id and wanting to behave nicely whether it's the id of a mobile worker, web user, or case (for example).

`get_doc_info` returns a DocInfo object that contains useful metadata about the doc in a consistent format. Interesting fields are

`display` --- like the username for a mobile worker
`link` --- link to main page for that doc, like a mobile worker's page in settings for a mobile worker
`type_display` --- like "Mobile Worker" for a mobile worker. This is translated text.

`{{ doc_info|pretty_doc_info %}` then gives a nice html display format that you can dump inline. See https://github.com/dimagi/couchforms/pull/72 for an example.