Define naming standard for error-correlation matrix parameterisations based on structure

[shunt16]

From Zhav Loizeau in #1:

I cannot not comment on “random” form because I reaaaaally wish it were either “un-correlated”, “independent” (this is not quite true as one can define un-correlated random variables that are dependent e.g., Image), or “diagonal” (to describe the shape of the matrix).

Still no standard in sight. As mentioned before, there is a Wikipedia page (why not).

[shunt16]

Discussion needed around what names to use for this parameterisations

[laurenth974]

Each Wikipedia page has a link to a corresponding Wikidata item (in the 'Tools' menu). Wikidata items have a unique identifier. The identifiers are supposed to be persistent. For example, diagonal matrix' unique identifier is Q332791. Probably a little bit closer to a standard than a Wikipedia page? Although debatle since Wikidata items are also crowdsourced not established in formal committees. Some Wikidata items do have links to external resources that are standards. For example, Hermitian matrix (Wikidata ID Q652941) has a link to the IEC vocabulary item 102-06-27.