Clean-up of countries class initialization
* Complicated data maps initialization routine broken up in favour of much easier to understand, smaller, single purpose, individual data map initialization routines
* Removes the possibility of two data maps being dependant on each other causing recursion
* Removed code that is no longer necessary
* Simplified initialization and clear data operations
* Removed unused internal function
* Cleaned up PHPDoc blocks

Retested WPSC_Countries API
* Fixed functions not working as a result of method name changes in prior commits
* Updated WPSC_Data_Map recursion prevention check to be fully re-entrant and handle cases where class was being constructed by multiple parents
Merge remote-tracking branch 'upstream/master' into pr-issue-1154-countries-class-init-cleanup
Merge pull request #1155 from JeffPyeBrook/pr-issue-1154-countries-class-init-cleanup

Clean-up of countries class initialization