Allow customize availabilities via docker environment variable

Hi. Can you add an environment variable AVAILABILITIES for the docker image to customize them please? Default values in the configuration file does not allow quarter, year nor none. I tried to set AVAILABILITY_DEFAULT to year but then it fallbacks to minute.

I think that an instruction env_2_cfg_string_array($cfg, 'availabilities'); should do the job in the file docker_config.php.

Thank you.