* ox.el (org-export-as): Allow {{{date}}} to take formatting-argument.
* org.texi (Macro replacement): Document {{{date}}} formatting.
* test-ox.el (test-org-export/expand-macro): Test {{{data(format)}}}
* org-NEWS: Mention optional {{{data}}} argument.
Optional argument to {{{date}}} like {{{date(FMT)}}} are treated
similar to {{{time(FMT)}}} if \#+DATE is a timestamp.