templates: edit_trait.html: Add extra fields for the form
templates: edit_trait.html: Add extra fields for the form

Add form elements for selecting group, type, and dataset. This mimics
the home page.

pjotrp/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,zsloan/genenetwork2,genenetwork/genenetwork2,pjotrp/genenetwork2,pjotrp/genenetwork2,zsloan/genenetwork2