decorators.py:
- DELETED: no longer have any custom decorators all uses of @require_project_user were replaced with view code

views.py:
- don't use @require_project_user decorator in panel views , use site model methods instead
- same for view_sample_scatterplot, sample_data, retrieve_compensation, retrieve_sample views

models.py:
- add Site method has_view_permission

view_project_panels.html:
- check user perms for add and edit links