[Delivers #47583279] Add asterisk image to any required or conditionally required form inputs

Introduced some CSS classes to help delineate required or conditionally required form fields.  Currently the new classes render a red asterisk for required fields and a grey asterisk for conditionally required fields.

I've also tweaked the subrecord form template to allow a tooltip to be added to a subrecord form section heading e.g. and I18n entry for "en.accession.dates_tooltip" will add a popup tooltip on the Dates section heading.