LP#2051944: Improve FMREC primary key column test

LP#2051944: Improve FMREC primary key column test

FMRecordEditorComponent was depending on the @reporter:datatype to
identify the primary key (identity) field for an FM class.  Instead, it
should check the field name against the @oils_persist:primary attribute
of the <fields> element, which gets around the special case of org unit
id having a declared datatype of "org_unit", and future-proofs against
other possible edge cases.

This commit does that.

To test
-------
[1] Update the Organizational Units page's form to include "id" as
    a visible field, a la bug 2051879.
[2] Note that the form display a selector.
[3] Apply the patch and recompile the Angular staff client.
[4] This time, the OU ID should display as a read-only number.

Release-notes: Makes it possible to display the org unit ID as a number on Angular record editor forms for editing org units

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>
Signed-off-by: Terran McCanna <tmccanna@georgialibraries.org>