Extend avatar-driver by extension in ACP not possible

Extending avatar-driver not possible in ACP user-management -> avatar

Problems because of
In acp_user around line 1849
$config_name = $phpbb_avatar_manager->get_driver_config_name($driver);

The config name comes from the class name of the driver.
As the function get_driver_config_name only regex for phpbb the whole class name of our driver is returned, for example forumhulp/avatar/driver

Next line adds acp_avatar_options_$configname.html so the script is looking for a template acp_avatar_options_forumhulp/avatar/driver.html in adm/style only

The filename isn't possible and for a extension it should also look in the extensions adm/style folder