Implement ``fetch'' action.

- Insert ``fetch'' before ``extract''.
- Add ``distclean'' to clean and also remove fetched files.
- Use curl(1) to fetch files if it's available, falling back to ftp(1).
- Add unit test for ``fetch'' action.
Add fetch URLs to pecan packages.
Add missing = in initializer.
Add additional lines for debugging a package.
Update ``git'' to 1.8.1.