type == file; extraData = size,sha1

    /opt/appfs/hostname/{sha1,package/os-cpuArch/version}/file
    	Fetches: http://hostname/appfs/sha1/<sha1>

Database
--------
    hostname_to_packages(hostname, sha1);
    hostname_to_packages(hostname, sha1, package, version, os, cpuArch, isLatest)
    package_info(sha1 PRIMARY KEY, package, version, os, cpuArch, isLatest)
    package_to_files(package_sha1, type, time, source, size, file_sha1, name)