Add LOCALE config settings

next to the current lang/encoding add locale that is a combination of
both.
Also add a locale folder constant

the default LANG variables (DEFAULT_LANG, SITE_LANG) change from en_utf8
to en_US
new DEFAULT_LOCALE with en_US.UTF-8

www/configs/config.other.php

@@ -21,7 +21,10 @@ $paths = [
 ];
 // find convert
 foreach ($paths as $path) {
-	if (file_exists($path . DIRECTORY_SEPARATOR . 'convert') && is_file($path . DIRECTORY_SEPARATOR . 'convert')) {
+	if (
+		file_exists($path . DIRECTORY_SEPARATOR . 'convert') &&
+		is_file($path . DIRECTORY_SEPARATOR . 'convert')
+	) {
 		// image magick convert location
 		define('CONVERT', $path . DIRECTORY_SEPARATOR . 'convert');
 		break;