Python 2.5 compatibilty for worker_thread

From: Benoit Pierre <benoit.pierre@gmail.com>

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1017 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Limit spawned threads in worker_thread.

From: Benoit Pierre <benoit.pierre@gmail.com>

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1018 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Improve and fix thumbnail generation in icon views.

From: Benoit Pierre <benoit.pierre@gmail.com>

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1019 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Improve responsiveness of page selector by not waiting for thumbnail.

From: Benoit Pierre <benoit.pierre@gmail.com>

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1020 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Update thumbnail preview when page becomes available.

From: Benoit Pierre <benoit.pierre@gmail.com>

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1021 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Invert if criteria to remove redundant return statement

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1022 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Use worker_thread in archive_extractor.

From: Benoit Pierre <benoit.pierre@gmail.com>

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1023 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Spawn multiple threads for calling external extraction tools.

From: Benoit Pierre <benoit.pierre@gmail.com>

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1024 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Add preference option to tune max extraction threads.

From: Benoit Pierre <benoit.pierre@gmail.com>

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1025 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Move language selection into appearance, consolidate threading and caching

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1026 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Updated translation template and German translation

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@1027 ef8490bc-f317-4725-81ed-e95a9aca1bcf