Make Sponsor province field optional

[iandunn]

In the Sponsors custom post type, the State / Province field is required, but not all countries have intermediate regions like that. It should be optional for those countries.

On an implementation level, the simplest way is to just make the field always optional, but add a note asking users to fill it in if their country does have them.

See ​https://wordpress.slack.com/archives/C08M59V3P/p1491641449095148

[davidmosterd]

Working on this right now. I have removed the required html attribute and added a description tag stating it's only required when your country uses states or provinces. I'll submit my patch in a moment.

[davidmosterd]

Initial fix

[davidmosterd]

Changed the context a little

[davidmosterd]

@iandunn Hows this for a first meta-ticket? :)

[davidmosterd]

Added not applicable as a default state

[davidmosterd]

In the https://meta.trac.wordpress.org/attachment/ticket/2711/2711.meta.3.diff I added a 'underwater' default state that is 'Not Applicable' to make sure it's always filled with something meaningful. It removed this string on the user-form to prevent them seeing the actual value.

[davidmosterd]

removed auto-formatting

[davidmosterd]

sneaked in high priority

[coreymckrill]

In 5575:

WordCamp Post Types: Make sponsor invoice province field optional

Some regions don't have a state or province as part of their official
address format. However, some banks always require that field on
invoices, regardless of the country. The solution in this patch is to
make the state/province field optional, but add the string
"Not applicable" if the field is left blank when the form data is
saved.

Props davidmosterd
Fixes #2711