List of stuff I want this module to have

  * on request, ignore unrecognized options in App::Getopt->options() method
  * on request, 1) ignore or 2) treat as non-option args unrecognized options
    in App::Getopt->cmdline() ((2) should make multi-level option sets
    possible)
  * on request, treat options without help message as unrecognized in
    App::Getopt->cmdline()
  * set other options when setting current one (opt { set => sub { ... } })
  * print --help message as table (`rsync --help' like, at least in options
    section)
  * add priority-based option lookup
  * add environment variables handling (those options will also get their prio)
  * set/change options later, at run time, using copy-on-write strategy
    (multithreading anyone?)

List of ideas to settle
  * how about whole subtree aliases? (for subsystem to have its own view on
    config options without arduous copying all the options)
