provide get_server_role() to abstract different roles and capabilities

include/identity.php

@@ -484,7 +484,7 @@ function identity_basic_export($channel_id, $items = false) {
 
 	// use constants here as otherwise we will have no idea if we can import from a site 
 	// with a non-standard platform and version.
-	$ret['compatibility'] = array('project' => PLATFORM_NAME, 'version' => RED_VERSION, 'database' => DB_UPDATE_VERSION, 'server_role' => UNO );
+	$ret['compatibility'] = array('project' => PLATFORM_NAME, 'version' => RED_VERSION, 'database' => DB_UPDATE_VERSION, 'server_role' => get_server_role());
 
 	$r = q("select * from channel where channel_id = %d limit 1",
 		intval($channel_id)

include/network.php

@@ -1805,6 +1805,7 @@ function get_site_info() {
 	$data = Array(
 		'version' => $version,
 		'version_tag' => $tag,
+		'server_role' => get_server_role(),
 		'commit' => $commit,
 		'url' => z_root(),
 		'plugins' => $visible_plugins,