Entry of concept "source" should allow entry of short form and long form sources for standards

[ronaldtse]

From glossarist/iev-data#62 .

ISO 10241-1:2011 contains some examples of source references with titles

although I agree that for a standard, one would not normally include the title as described in ISO 10241-1:2011, 6.8, but this is only a recommendation: “The indication of the source should be in coded form and a link or reference to a standard bibliographic description provided.”

Meanwhile, since the rules do not prohibit the inclusion of a title, we should not either.

Maybe you should allow for a short form (without a title) and a long form (with a title) of an xref, where the short form is the default?

So we should allow for a short form (without title) and also a long form (with title, even in the case of a standard), depending on user preference.

Technically, we should allow entering references in ISO 690 format because ISO 10241-1 accepts only the ISO 690 bibliographic format.