Updated strong_params to accommodate an extra string being created if I allow for nested strings to be passed during the create action.

Edit action uses pv_array_test_params which accommodates nested
string_test for updating string tests individually on the
edit_pv_array_test page.
Changed after_create back to after_init
Fixing up form partial for pv array test.
Added string_tests partial for editing strings individually
changed what's available for editing
Changed the way the new page uses the form partial
Removed redundant links on the show page and adjusted the view slightly
language changes
Last commit before nesting resources
Added string_test_cell partial for string_test partial in pv_array_edit