fix Facebook invite, had wrong list of UIDs
invite list is empty when there are no 1st degree locals. in this condition, allow invite to be any 1st degree.
show loading icon when a user selects a location so that during the jQuery post it's clear something is working.
assign puts current url in the session history
on mobile, open message dialog in new window. remove this attribute on desktop so that it doesn't open new window to '#' and also the Facebook modal.