some improvements

* handle exceptions in multiprocessing
* readme update
* safe logger handler implementation (uses either stderr or
  rotatingfiles)
* user UID check

package/etc/ahriman.ini.d/logging.ini

@@ -2,17 +2,11 @@
 keys = root,builder,build_details,http
 
 [handlers]
-keys = console_handler,build_file_handler,file_handler,http_handler
+keys = build_file_handler,file_handler,http_handler
 
 [formatters]
 keys = generic_format
 
-[handler_console_handler]
-class = StreamHandler
-level = DEBUG
-formatter = generic_format
-args = (sys.stdout,)
-
 [handler_file_handler]
 class = logging.handlers.RotatingFileHandler
 level = DEBUG