Bug#1098672: fails with PYTHONSAFEPATH

[VA]

Package: trimage
Version: 1.0.6-2


When running a game with PYTHONSAFEPATH=y, this error occurs at start:

```
Traceback (most recent call last):
   File "/usr/lib/python3/dist-packages/trimage/trimage.py", line 16, in 
<module>
     from ThreadPool import ThreadPool
ModuleNotFoundError: No module named 'ThreadPool'
```

This is because the code does absolute imports not using the package 
name while in a package:

/usr/lib/python3/dist-packages/trimage/trimage.py contains

`from ThreadPool import ThreadPool` while it should be either:

- `from .ThreadPool import ThreadPool`
- or `from trimage.ThreadPool import ThreadPool`

Also, the runner in /bin is rather unidiomatic, it starts a second 
python interpreter within the first.