Configuration for Non-US Address Formats + Country Availability Limit

1. Add Locale-specific Address Format section to config file.
1.1 CIVICRM_ADDRESS_FORMAT setting defines the order (pattern) of address elements for addresses input and display for the current installation.

1.2 This setting will contain a list of civicrm address object property names. Default values (US pattern) would be:
'street_address, supplemental_address_1, supplemental_address_2, state_province, postal_code, postal_code_suffix, country'

1.3 All code for input (form) and display (page) of address blocks uses the list to control field order. We should have the US pattern as a hard-coded default (if this setting is blank or missing).

2. Add Country Availability section to config file.
2.1 Functionality is similar to Province Availability - if setting is blank all countries are included in Country select values. Else, user may enter a comma-separated list of one or more ISO country codes and the select values are limited to items in the list.