api_view.py:
- created LoginRequiredMixin to require the user be logged into the site
- created PermissionRequiredMixin to ensure that only resources for projects to which the user belongs are shown...only works on DetailViews
- restrict ProjectList to user projects
- SampleList now restricts to user projects, and has filtering for multiple names along with the site and project

serializers.py
- added site and project as fields in SampleSerializer