[Linked fields] Add Linked Field as a custom field type (#1563)

* Add linked fields support

* Fix style, don't show linked field if Secure Note

* Finish basic linked fields for Login

* Use Field.LinkedId to store linked field info

* Reset Linked Custom Fields if cipherType changes

* Refactor to use ItemView class

* Use enum for LinkedId

* Detect if no linkedFieldOptions

src/Core/Services/CipherService.cs

@@ -1190,7 +1190,8 @@ namespace Bit.Core.Services
             {
                 var field = new Field
                 {
-                    Type = model.Type
+                    Type = model.Type,
+                    LinkedId = model.LinkedId,
                 };
                 // normalize boolean type field values
                 if (model.Type == FieldType.Boolean && model.Value != "true")