Making call to DnsRequest more explicit.

Use DNS native Type for qtype when calling DnsRequest()

On a poorly configured apache, it seems the unicode literal that we pass as
qtype doesn't get converted correctly. This saves the internal DNS code from
having to do the conversion from string to int and is more robust against
poorly configured apache mod_wsgi setups.

Bugs closed: 3656

Reviewed at https://reviews.reviewboard.org/r/6552/
Fix typo in the default encoding name

The default encoding for repositories (if utf-8 fails) was `iso-5589-15`, which
isn't valid. The correct one is `iso-8859-15`.

Testing Done:
Encoding names were tested in the Python shell

Reviewed at https://reviews.reviewboard.org/r/6561/
Stop accepting group display names in target_groups on a draft in the API.

The API for review request drafts was allowing target_groups to match up
group display names. This was here for old legacy reasons, but is
undocumented, and it's very unlikely anyone is making use of it anymore.
(If they are, they'll have to adapt.)

The main reason this was a problem was that a group could have a display
name matching another group's ID, which would result in an error in
adding that group. That case was confusing and non-obvious, and worth
making the above change.