uasyncio.queues: Add simple implementation of asynchronous queues for uasyncio

Hi, I've added simple port of asyncio.queues.Queue. It can be a bit slow, but works well for me.
For testing:
```bash
cd uasyncio.queues/tests
micropython test.py
```
Well, the current issue is that "test_*" are named both unittests and non-unittests, e.g. https://github.com/micropython/micropython-lib/tree/master/os , so the problem is what to rename non-tests too...

Btw, I personally prefer Python approach to testing, not Java ;-). With it, test discovery is trivial - files named "test_*", containing "test_*" functions inside are tests.