Fixed some issues and added partial support for Windows

Changes:
- Fixed Akeneo logo image.
- Added support to import CSV on Windows.
Ouch, I think this line kills kitten ;)

But it makes sens for windows to not use /tmp/. I think a better way would be to have a constant with 'export_%datetime%.csv' and in the getFilePath() check if the $this->filePath is empty, and if yes, then use the constant and the sys_get_temp_dir() to return a value.