#23 Add more MIME types to the desktop file, fix exec line

[Balló György]

This patch fixes the following problems in the xarchiver.desktop file:

• Add %f suffix to the exec line in .desktop so file managers will recognise that Xarchiver could open files.

• Xarchiver is able to open more file formats than currently defined in .desktop file, so add them to MimeType list: LZMA, LZMA.TAR, LZOP, LZOP.TAR, XZ, XZ.TAR, DEB, RPM.

• The 'multipart/x-zip' shouldn't be used (non-standard), so remove it from the MimeType list.

Can be applied to xarchiver 0.5.4.