Redhen filtering requires default

Problem/Motivation

When filtering by contacts or organizations that include an address field, contacts for countries other than the default country are never show.

This bug results from changes in #1801390: Use native field API to generate filters in redhen_filter_form. Because the AJAX operation triggered when the country was changed on an address broke form submission, the country select was hidden (access = FALSE). However, this means that a country is still assumed, and because it cannot be selected, the default site country (if set) is used.

Proposed resolution

There are two distinct problems here.

Problem 1: A country is always selected, meaning it's never possible to show contacts from all countries.

Possible fixes:

1. Add an "Any" country option so that it's possible to skip the country filter.

Problem 2: The default country is always selected.

Possible fixes:

1. Troubleshoot and fix the AJAX callback issue so that regular address functionality is restored.
2. Restore access to the country select but limit it to "Any" or the default country, with "Any" the default.
3. Restore access to the country select and allow all options. The form will be semi-broken, however, as it won't be rewritten to be appropriate for the selected country.

Clearly option 1 here is preferable, but 2 might be an acceptable short term workaround.