Exp and windows: rethinking any matching

@philippkeller this PR provides changes according to the last comments in #24.

You can diff it against the exp_and_windows branch to see the changes or look at the d9f868b commit.

Expanding the macros produces plain if/else structure.

One of possible ways to keep an interface 'pretty clean' is to create a macros instead of providing ABInterest and or stuff. There still no additional copies and using index which allows to rely on the idea that all path of code are covered.

I didn't test the macros highly.

For 2 days I was thinking about what type of macro could help here and came with that.

One of possible solutions could be usage of tuple (A, B) and implementing for a reasonable number of tuples Needle trait with implementation according to pick first logic.

There also was an idea creating a new struct(A, B, C) and a result enum(_1(AResult), _2(BResult), _3(CResult)) by macros including a fact that it will shadowing in in internal scope it will be OK and would work but ...... I tried it and didn't manage to do that. What's more to notice in this approach creates a 'generable' enum variants which is not so perfect. And truly saying I am not even possible if it's possible to be done by macros in rust.

The problem with using some structure like Vec<dyn Needle> is that here we should specify a associative type. But we can't spicify it to something dynamic as I understand. That's why returning an index is not so simple :)

I've not found a better solution yet.

rust-cli / rexpect

Exp and windows: rethinking any matching #27