LP2050227: Update fm_IDL.xml required fields

LP2050227: Update fm_IDL.xml required fields

Add the oils_obj:required="true" attribute to the IDL fields that are
actually required by the database.  A required field is one that
derives from a base table column that has a "NOT NULL" constraint and does
not have a default value.

IDL objects that are virtual or read-only are skipped as are virtual
fields.

Fields that already have the oils_obj:required attribute set are not
changed, even if the fields do not meet our criteria for being
required.

Signed-off-by: Jason Stephenson <jason@sigio.com>
Signed-off-by: Galen Charlton <gmc@equinoxOLI.org>
Signed-off-by: Jane Sandberg <js7389@princeton.edu>