Rename emergency contact information

AC cannot collect emergency contact information, so the labels need to
be changed.
Make emergency contact optional

Uber now only validates the emergency contact name and number if
COLLECT_INTERESTS is turned on. This config option was used so we have
one point of contact for all the generic fields being turned on and off
- these should be replaced by a new system soon.
Merge pull request #662 from magfest/change_ec_labels

Change Emergency Contact Information