Add visual clue to typography for quotation tags

[alerque]

OSIS files that tag OT quotations in the NT should be rendered with a distinctive visual style by default.

See also #845 for a related rendering issue.

See also discussion on this OSIS converter issue.

[DavidHaslam]

This prompts the question as to which style should be used?

• Some translations use italics.
• At least one uses oblique (subtly different to italics).
• The NASB uses small-caps.

How important might it be to approximate to how the printed editions look for copyrighted works?

Should this be implemented using an ancillary style sheet taylored to the module requirements?

[karlkleinpaste]

the problem is that, as for #845, we would depend on libsword to offer an OT quotation class that could be distinguished visually. until libsword does that, there's nothing we can do about it in xiphos.