Remove `Location.map_embed_code`
Remove `Location.map_embed_code`

Limit how many radically different ways you can
define a Google Map item.

If we need to display an arbitrary HTML embed
item we already have content items to do that,
let's not accept this junk in the GoogleMapMixin.

ic-labs/django-icekit,ic-labs/django-icekit,ic-labs/django-icekit,ic-labs/django-icekit