Document use of package name globs; fix two minor errors.
Allow use of installed package names with globs instead of portnames, see issue #5.
Minor: adjust indentations.
Migrate from deprecated optparse module to argparse.
Delete an unused option and a related function.
Update port, delete generated file.
Rework command line options.
Remove unused (actually always used) -A option.
Refactor: separate dirs and files to ignore in params in latest_mtime().
Do not check mtime of files not affecting dependences.
