Symlink option

- Converted commands to optparse
- Added `--symlink` and `--no-symlink` options to `pip2pi` and `dir2pi`. I need to create a local PyPI on Mac and Linux machines, which will be checked into Git, then used on Windows machines. Msysgit doesn't support symlinks, so I have to *copy* files into PACKAGE_DIR/simple/. Since the copy resolves to the same file object, as they have identical hashes, no space is wasted in Git.
Please change to `OS_HAS_SYMLINK`