BRCD-1770 lines custom fields - add option to add\remove\edit foreign fields
To avoid bugs its impossible to change existing fields entity and field fields. In edit mode possible to change only title and translate. In addition its not possible to create more then one foreign field from same entity and same field.
This will prevent duplicate fields with same field_name because field name build from "foreign + entityName + fieldName" and will support old foreign fields that was build manually.