Decompression should always use temporary directory and/or filename

[pnuu]

Currently decompression of bzip2 in Trollmoves Client does the decompression directly to the target directory with the actual filename. This can cause complications if those files are further transferred/handled by Posttroll-agnostic scripts.

The files should be decompressed to a temporary name (even in temporary directory?) and then moved/renamed to the correct location/filename. Same should be done with every decopression type. I believe xRITDecopress already works like this.