mostly just formatting for PEP8 styles

api_views.py:
- in SampleList view method post, only need to replace the response data if we applied a panel, moved inside the try block
api_views.py:
- added views PanelList, SubjectList, and SiteList

models.py:
- added name property to PanelParameterMap as the hyphenated combo of the short name and value type

serializers.py:
- added serializers:
       PanelParameterSerializer
       PanelSerializer
       SubjectSerializer
       SiteSerializer