Ffconverter

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* Added zip to input formats

* No longer assuming bzip is present

* Added tar.bz2 as in- and output format

* Creating a tar archive will no longer add the directory structure
'/tmp/ffconverter' on top

* Will no longer disable compression entirely if a single compression
dependency is missing

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* Added option to decompress to a folder

* Fixed Translations not working

* Some other minor fixes

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* Added pandoc, zip, tar, ar, squashfs-tools

* Added "All Formats" tab

* Removed "Documents" tab

* Renamed all "ffmulticonverter" to "ffconverter" to allow having both the fork
and the original installed

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* PyQt5 port

* User can now specify a custom ffmpeg path.

* Libav/avconv support dropped.

* Progress bar showing total conversions progress removed.

* Document tab now allows all conversions supported by unoconv.

* Shutdown after conversion button added.

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* Minor fixes and changes.

* Updated translations.

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* Compatibility bug with pyqt 4.11.4 has been fixed.

* Compatibility bug with python 3.2 and previous versions has been fixed.

* New Image Preferences: default convert options and extra image formats.