paper: Remove auto-generated PDFs

The Makefile will be generate these from the SVGs as needed.
Makefile: Add rules to build PDF graphics and the final paper

The PDFs are generated without the .svg.pdf extension, so I also
tweaked the paper source to reflect that.  Build from scratch with:

  $ make

and clean up afterwards with:

  $ make clean
Merge pull request #30 from wking/makefile

Add a Makefile to build the paper automatically