Code review comment for lp:~cprov/launchpad/bug-404144-unicode-ppa-searches

> It consists of changing query_string_parameters() to already decode variables,
> and on the Distribution:+search view we can simply use the original form
> QUERY_STRING, instead of rebuilding it with urlencode.

As we discussed on IRC,

1. Please don't use setdefault at line 23, because we already know there's no value for that key
2. Please add a line break at line 28
3. Please clarify that get_query_string_params returns lists of unicode strings in the docstring.
4. Please explain that the doctest at 188 would raise an exception if the value weren't utf-8 decoded (e.g. "The 'name_filter' is decoded as UTF-8 before further processing. If it did not, an exception would be raised.")