HGE: Add connectedCallback back in to get SGE form Template
HGE: Add connectedCallback back in to get SGE form Template

Removing the connectedCallback broke the form when used in single gift
mode.  This change puts it back and de-duplicates the form
initialization code so that both modes can use the initializeForm
function after retrieving the Template JSON.

SalesforceFoundation/Cumulus,SalesforceFoundation/Cumulus,SalesforceFoundation/Cumulus,SalesforceFoundation/Cumulus