Bug 20564: Don't use system to unzip files

Bug 20564: Don't use system to unzip files

To test:
1 - Setup a zip file for patron images and cover images
2 - Test each tool
3 - Get a '500 error' after upload (note images do upload and attach)
4 - Apply patch
5 - Restart all the things
6 - Test agtain, uploads should complete and results display

Signed-off-by: George Williams <george@nekls.org>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>