let's support more DRF view types

[Abdenasser]

@elmkarami @yezz123 I'm thinking about adding support to more view types for example if someone wants to have a ViewSet with mixins he'll pass an option to the command and we'll pick the right template based on that option, let's say he selected mixins python manage.py dr_scaffold snippets Snippet body:textfield -LC--mixins where the LC refers to List and Create mixins, then we generate this:

from snippets.models import Snippet
from snippets.serializers import SnippetSerializer
from rest_framework import mixins
from rest_framework import generics

class SnippetViewSet(mixins.ListModelMixin,
                  mixins.CreateModelMixin,
                  generics.GenericAPIView):
    queryset = Snippet.objects.all()
    serializer_class = SnippetSerializer

    def get(self, request, *args, **kwargs):
        return self.list(request, *args, **kwargs)

    def post(self, request, *args, **kwargs):
        return self.create(request, *args, **kwargs)

Let me know what you guys think ?