PASSAGES: Allow user to add passage references not available for a language

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Allow user the ability to add NT Survey RG passages and OT Survey RG passages to a document even if the language doesn't support those passages. They will be shown in the UI but as disabled if not actually provided by the language. They will be shown in the generated document as a disabled/greyed reference with no accompanying passage text if the language does not provide that passage. The reasoning from the PO is that on-site this may be desired as perhaps someone can provide the text at that time even if it is not yet availalbe in USFM.