User should be able to choose the temporary directory

[Marco Rodrigues]

This bug was reported in Debian.

I'm unable to download and install any dictionary (except the small
Srujanika Science Glossary, which is of no intereste to me...) because
I don't have enough free space in the /tmp directory.

Moreover there is no information that the download failed, just the
confusing message:

extracting '/tmp/./stardict-dictd_www.dict.org_gcide-2.4.2.tar.bz2' to: /tmp
Traceback (most recent call last):
  File "/usr/share/babiloo/core/dictionary/engine.py", line 54, in loadDictionary
    dictionary = extracted_file_sizes[-1][1]
IndexError: list index out of range