Add Util::Fork; Parallel::ForkManager-derived fork mgr

	new file:   lib/Kodiak/Util/Fork.pm
Util::Fork; fix on_finish callbacks

per-PID callbacks like ForkManager; also pass $tag to callbacks.

	modified:   lib/Kodiak/Util/Fork.pm
Stash POD

	modified:   lib/Kodiak/Stash.pm
doc/ updates, some outline wrt useflags

	renamed:    doc/spec/example-1.2.3.kodi -> doc/example/example-1.2.3.kodi
	new file:   doc/example/profile/useflags.global.yml
	new file:   doc/example/profile/useflags.perpkg.yml
	new file:   doc/style.txt
Kodiak POD outline

	modified:   lib/Kodiak.pm
Stash->exists()

	modified:   lib/Kodiak/Stash.pm
	modified:   t/01_base/stash.t
Util::Fork; use ::Stash

	modified:   lib/Kodiak/Util/Fork.pm
Util::fork test (+ fixes for working run)

	modified:   lib/Kodiak/Util/Fork.pm
	new file:   t/02_util/fork.t
Base; import reftype

	modified:   lib/Kodiak/Base.pm
Tree; filter_via should probably just take a coderef

	modified:   lib/Kodiak/Pkg/Tree.pm
Pkg; proper pkg atom creation

	modified:   lib/Kodiak/Pkg.pm