Add locale.maxTaskPar, adjust dataParTasksPerLocale.

Add documentation for the locale.maxTaskPar method, and document that
the default value of dataParTasksPerLocale is the .maxTaskPar for the
top-level locale.
I don't think we use this style of reference with no leading text anywhere in general.  I'd change it to something like `(See~/rsec{Locale_Methods})` or something like if it doesn't make the table look too funny.