While starting to implement this, I found a number of deficiencies:

- Drop regular expressions. As it turned out, only very few fields for
  instances used them, all of which can easily be turned into static
  field names.
- Use two separate calls with a request and response description each.
- Add forgotten list of fields to query request.
- Add value status for case where a field is not available for an item,
  e.g. NIC 3 for an instance with only one network interface.
- Add "timestamp" field type.
- Updated examples.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>