Vue binding for environment role selections.

The environment name will be grayed out until something besides the
default "no access" is selected.

Small changes to the application member subforms:
- filter for "None" as a string
- have nested forms inherit from FlaskForm; each nested form adds its
  own validation error flash otherwise if there are validation problems

js/components/options_input.js

@@ -18,6 +18,7 @@ export default {
       showError: showError,
       showValid: !showError && !!this.initialValue,
       validationError: this.initialErrors.join(' '),
+      value: this.initialValue,
     }
   },