Validate the phone number box is filled out

Checks if the phone number field is empty, regardless of staffing
status.
Fix birthdate for placeholder attendees

Forces blank birthdates to None value, which the database will accept,
in order to prevent 500 errors when saving placeholder attendees.
Update model_checks.py
Remove check for SUPPORTERS_ENABLED

Since we've decoupled the kick-in levels from the supporter_level, the
options were hidden (or didn't work). This should reinstate them.
Merge pull request #736 from magfest/fix_kickin_levels

Remove check for SUPPORTERS_ENABLED
Merge pull request #732 from magfest/fix_validations

Fix validations
Fix javascript badge boxes

Fixes the Anthrocon badge boxes so the correct one will be selected,
based on the amount_extra.
Fix staffing checkbox JS error

Prevents the system from checking a currently non-existent staffing
checkbox by hiding the function call behind COLLECT_INTERESTS.
Merge pull request #738 from magfest/fix_javascript

Fix javascript errors
Hide Affiliate form

Hides the affiliate form behind COLLECT_INTERESTS, since AC doesn't want
it.

Also includes a minor improvement to the Javascript in the pre-reg form.
Replaces dealer checkbox and hides it

Reverts the dealer checkbox back to the canspam checkbox, and hides it
behind COLLECT_INTERESTS.
Merge pull request #740 from magfest/remove_affiliates

Hide Affiliate form
Merge pull request #741 from magfest/remove_email

Replaces dealer checkbox and hides it
Remove text reference to "Full weekend pass"

Changes the index page to say "Membership for Anthrocon" instead of
"Full weekend pass."
Pre-reg form text changes

Changes "con" to "convention," and adds a text notice about dealer
registration.
remove old Mag-specific analytics code
Add custom price-change text

Adds custom text to describe a single price change. Requires a new date
setting called first_price_bump.
Merge pull request #745 from magfest/change_text

Custom AnthroCon text changes
Replace hard-coded URL

Replaces the hard-coded MAGFest contact url with a new variable.
Merge pull request #746 from magfest/change_text

Replace hard-coded URL