adds TextField to hq crispy
only initialize select2 if field is not hidden
fetch version of current plan
more useful __str__ for plan version
initial cleanup of Subscription form ui
use select2 for billing account and software plan version fields in new subscription
remove is_active field from form
final cleanup of styles and links in new subscription form
Merge pull request #2783 from dimagi/plan-version-improvement

Improvement of New Subscription form