Support reloading containers

[ihrwein]

Docker's kill parameter cand send a SIGHUP signal to a container, which should reload most programs.

It'd be nice to have a fig reload <service> command or extend it's kill parameter with -s --signal <SIGNAL> options.

I would use it after a fig scale to reload an nginx reverse proxy.

[aanand]

+1 for docker kill -s.

[ihrwein]

Thanks! :)

[albers]

Which signals would make sense in this context?
I already added SIGHUP SIGINT SIGKILL to the bash completion (#639).

[ihrwein]

I think those three covers the most use cases, but maybe SIGUSR1 and SIGUSR2 would also be helpful.