move to the new uproxy-lib world

This moves the repo to the new `uproxy-lib` world (4.x.x).

Summary:
* add per-module typescript definitions
* move samples under the modules-under-test
* add a `tsd/` tree
* update imports

This also kills the `copypaste` sample. I was planning to do that in my next merge but since it's a bit of work to migrate to the new build system, I opted to do it now. Also, you might point out that while the `chat` sample is under `pipe`, it doesn't actually use `pipe`. Well, my next pull request will make that clearer :-)

Tested by `grunt test` and manually exercising the sample apps.
OK. I was thinking of the case where a dependant of `uproxy-lib` needs some _other_ `tsd` import(s).

Then it gets messy because I don't see how we can fully automatically "merge" two repositories' typings, due specifically to this file:
https://github.com/uProxy/uproxy-lib/blob/dev/third_party/typings/tsd.d.ts

Not currently an issue for `turn-relay`, of course, so I'm happy to remove this directory.