Extend skogul.Identity and merge with logging

[KristianLyng]

What I want is for modules to be able to have something like:

func (f *Foo) Send(...) ... {
    skogul.Log(f, "whatever")
}

and have skogul.Log look up f to find the name, which we have now, but also the family (receiver/sender/etc) and implementation (http/net/file/sql). It would significantly reduce boilerplate for logging and at the same time enrich the log data noticeably.

Or something of the like. It means slightly extending skogul.Identity, which really isn't a problem. Today, it's map[interface{}]string, if instead, we add a ModuleIdentity type:

type ModuleIdentity struct {
    Name string
    Family string
    Implementation *skogul.Module
}

That could be used instead (slightly unsure about Implementation, but worth considering). I imagine there are other benefits too.