Cleanup and simplify the Linux build script

1. Use python setup.py sdist instead of building the tarball by hand
2. Store resulting packages in a single 'packages' directory
3. Some minor cleanup/simplification
Move to bundle_files = 3

bundle_files = 1 or 2 was causing build failures.

Solution: switch to bundle_files = 3 and use Inno Setup to build
a proper installer.
Merge pull request #164 from ethanwhite/update-release-script

Cleanup and simplify the Linux build script