Transparent (de)compression

This is a large MR but brings significant improvements:

• All (de)compression is done transparently in-process
  • Detected from the file extension for outputs
  • Detected from the file extension and/or file magic for the standard input
• Removes a huge footgun in that you can specify a archive.tar.gz but without specifying compress it will actually create a tar
• A new //tar/tool provides a central tool for general tar manipulation
• The tar_concatenate/tar_filter rule implementations become simple due to //tar/tool accepting input/outputs as arguments
• Hopefully, improvements in speed as it removes the need for all the pipes