Windows support

[Michal 'vorner' Vaner]

Currently, the crate supports only unix systems. Part of the functionality could be useful on windows and there is sure to be some way windows services start as services. It would be great if we could also support windows.

First phase

There are some unix-specific things in there ‒ the signals and unix-specific daemonization. These could be just removed and made unavailable. It would be up to the user of the crate to do something meaningful and ask for configuration reloading when relevant, but it would at least compile.

This probably should also make the configuration option about daemonization disappear on windows.

Second phase

Someone who knows how it works on windows could provide similar platform specific routines & config fragment.