Amend registerItem lifecycle to better suit WMO governance process

[6a6d74]

The standard lifecycle for register items is:

Submitted > [ Experimental | Stable ] > [ Deprecated | Retired ] > Invalid

WMO want to both change the names (labels only?) of the statuses and add another interim status:

Submitted > Validation (Experimental) > Preoperational > Operational (Stable) > [ Withdrawn (Deprecated) | Retired ] > Invalid

A software change maybe required, but there may also be a work around.

[6a6d74]

Furthermore, it now seems obvious that we need a withdrawn status to indicate that a term or register has been withdrawn before operational implementation following a period of experimentation.

The movement of code table C-15 to D-2 provides an example. We still want the old /common/c-15/... URIs to be valid so that they can provide a redirect to the new /common/quantity-kind/... URIs.

[domlowe]

Might be worth looking at the spec again too? Although the current labels are more useful imo (experimental in particular).

RE_ItemStatus:

notValid - The item has been entered into the register, but the control body has not accepted the proposal to add it.

valid - The item has been accepted, is recommended for use, and has not been superseded or retired.

superseded - The item has been superseded by another item and is no longer recommended for use.

retired - A decision has been made that the item is no longer recommended for use. It has not been superseded by another item.