Add signup embed to host tools

[christineletts]

• Embed event signup page
• Set redirect/refresh so it goes back to signup, not attendee tools
• Only show signup section in embed (not event, header/footer, etc.)
• Mark signups through host panel attended (or similar) - use ?source=onsite
• Create a way to join advocacy teams through host panel
• Ask AK about displaying custom action fields on event roster
• Refresh parent page on signup submit
• Send a follow up email to Maiya/Emily asking them to add AT members and resending the link.
• Sort attendees by name
• use request.GET.hidewrapper and request.GET.selfredirect to hide wrapper and redirect

[christineletts]

#160 #159

[christineletts]

Still would like to refresh parent page on submit of embedded event signup. But the MVP is there.