Fix api views discovery when using "nested" urls

I often use include when writing my project urls.py. When i had something like this in my project:

```python
urlpatterns += patterns('',
    url(r'^api/v1/', include("api.urls")),
)
```
`DocumentGenerator` could not find my patterns. Its because it didn't look inside `RegexURLResolver`. I fixed this and now it looks recursively inside urlpatterns tree.

In addition i made generator to filter duplicate-named views, because `django-rest-framework` adds automatically some new patterns when you use `.format_suffix_patterns()` helper. It shows only views with shortest regex pattern.