Deprecate psutil.get_process_list()

_From [g.rodola](https://code.google.com/u/g.rodola/) on June 02, 2012 21:47:26_

```
Reasons: 
- it is just a one liner (return list(process_iter()))
- process_iter() should be preferred in general
- it's not even documented

We can deprecate it in 0.5.0 and get rid of it in 1.0.0.
```

_Original issue: http://code.google.com/p/psutil/issues/detail?id=273_
