make filelogger paths configurable

[DanielOaks]

so peeps can do user/network/destination/yyyy-mm-dd.log or user/network/destination.log or however they want to store it. make the default a middle-ground that makes sense, but with a few other options commented out in the config file.

we'll wanna make this depend on the config file because we don't want every user being able to mess with filelogger paths and possibly being dodgy with their own ones. use format strings or similar, like "%user%/%network%/%destination%/2006-01-02.log" (the time package's default format string format).