Draft: Refactor ads::client::{Client, Source} && apply fixes to adstool to better handle edge cases

[cartercanedy]

The semantics of ads::Source::Auto and the documentation seemed unclear with respect to configurations where there is no local router and the client is connecting directly to the remote ADS server or the client is using a local router to connect to a remote machine.

This PR updates both the documentation and adds a new Source::AnyLocalIp variant (which behaves identically to Source::Auto) for the core library, and updates adstool route so that remote route management functions properly with more edge-cases.

note: this PR is stacked with #39, will rebase to get rid of the extra commits once it's merged

[birkenfeld]

If you don't mind I'll review this once the other PR is merged :)

In general, I don't understand the reason to rename Auto to Any well enough; if it's intended to make it more clear, wouldn't something like LocalIp be more descriptive?

[cartercanedy]

wouldn't something like LocalIp be more descriptive?

yep, changed it

[birkenfeld]

Thanks, but I'm still not sure why "any" local IP? It's exactly the local IP isn't it?

Do you think it's also a good idea to provide something like LocalIPWithRouteAdded? Or too much feature creep and better to let users call add_route themselves?

[cartercanedy]

Honestly, I'm looking back at this PR and I can't remember how to reproduce the auth issues that I was seeing. I don't really think that there's a whole lot here besides some minor fixes that I can cherry-pick into their own separate PRs. Let me know what you think @birkenfeld, but I'll get started working on breaking up the changes into smaller diffs in the meantime