Adjust config:
Replace deprecated legacy_ssl with c2s_direct_tls.
Removed use_libevent = true. This means the default is now used which is epoll.
Added a test to check that no deprecated config settings are used.
Fixes#55 and fixes#56:
* Add environment variable HTTP_UPLOAD_FILE_SIZE_LIMIT for setting http_upload_file_size_limit
* Add environment variable HTTP_MAX_CONTENT_SIZE
* Add domain_http_upload to disco_items to support http_upload on some clients and if http_upload is not a subdomain
