Use `task id:… op` and `task uuid:… op` for robustness

[taskwiki](https://github.com/tbabej/taskwiki) tests uncovered that some UUID aren't parsed as UUIDs:

```
$ task 0003717d-b325-4fd1-8367-7492996250df export
Cannot subtract strings
$ task 0000000d-000a-0000-0000-000000000000 export
Cannot subtract strings
$ task 0000000d-0000-0000-0000-000000000000 export
The expression could not be evaluated.
```

This was reported to taskwarrior as https://github.com/GothenburgBitFactory/taskwarrior/issues/2306 but looking at the project activity I'm afraid it might stay unfixed for a while, and I'm not feeling confident enough to reorder the lexer myself. Therefore I suggest that tasklib use a more explicit form of filter to avoid hitting this bug.

So I'd suggest to alter https://github.com/robgolding/tasklib/blob/670836f56f8072cae112c4d1bf1b872472150b50/tasklib/backends.py#L408 (and a few other places) to include an explicit `uuid:` or `id:` prefix to help the taskwarrior parser do the correct thing.