* Use systemd socket activation
* Pass a new command line argument --systemd-socket-activation to the daemons if running on Linux
* Install .socket files
* Systemd services depend on their sockets
* Implement sd_listen_fds in OCaml
* Set FD_CLOEXEC in sd_listen_fds
* README: add comment about socket paths
* Linux systemd scripts: Rename albatross_stat -> albatross_stats
- console creates the run directories (albatross albatross/fifo albatross/util)
-> log depends on console
- albatross/fifo needs special permission (albatross_daemon creates fifo there, albatross_console needs to read them)
- use /var/lib/albatross/albatross.log for the log file
- only require root in albatross_daemon, use user albatross in albatross_console and albatross_log
- defer albatross_stat for now