ews: add ews_beta configuration alias

Add ews_beta configuration directive with the same effect as ews_experimental.
ews_beta takes precedence over ews_experimental.

exch/ews/ews.cpp

@@ -450,6 +450,7 @@ void EWSPlugin::loadConfig()
 
 	cfg = config_file_initd("ews.cfg", get_config_path(), ews_cfg_defaults);
 	cfg->get_int("ews_experimental", &experimental);
+	cfg->get_int("ews_beta", &experimental);
 	cfg->get_int("ews_pretty_response", &pretty_response);
 	cfg->get_int("ews_request_logging", &request_logging);
 	cfg->get_int("ews_response_logging", &response_logging);

exch/ews/exceptions.hpp

@@ -140,7 +140,7 @@ E(3017, "failed to get user permissions");
 E(3018, "insufficient access rights");
 E(3019, "failed to load calendar");
 E(3020, "failed to query calendar");
-E(3021, "request is marked experimental and can be enabled with 'ews_experimental = 1'");
+E(3021, "request is marked as beta and can be enabled with 'ews_beta = 1'");
 E(3022, "failed to get folder entry id");
 E(3023, "failed to get folder properties");
 E(3024, "failed to get item entry id");