Inconsistant behaviors between the WEB UI and the REST API: Item Specifications

[hajimeMU]

We can update Item Specifications definition with the WEB UI.
E.g., We can add new fields. The WEB UI then shows the newly added fields, BESIDES the old fields.
While this might be a strange behavior, this allows us to enter to those newly added fields nevertheless.

On the other hand, we are not allowed to enter to the newly required fields throug the REST API.