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

styles/sections/_application_edit.scss

@@ -85,3 +85,8 @@
 .environment-roles-new__head {
   font-weight: $font-bold;
 }
+
+.environment-name--gray {
+  font-weight: $font-normal;
+  color: $color-gray-medium;
+}