Type / subType fields, reduce subType to (single link) ForeignKey and customize display widget in form
copy over javascript Change Form (non-functional)
include javascript commands
dynamic showing and hiding of Dna form fields depending on selected Category
pre-populate Category field if form is called with existing object;
set initial values to Plasmid / generic plasmid
commit missing change_form with all javascript
add generic plasmid and insert sub-type
hide insert, marker, backbone by default
filter Insert and Backbone input by type
filter and adapt marker field