Added package management system detection.

@{*-core/*-test/*-package_manager} now capably detects all package management
systems of interest to zeshy (namely, all such systems also performing
dependency resolution, which aside from the notable exception of Slackware-
derived distributions is effectively all of them). Also added
:set_list_to_vars_global() and :set_list_to_vars_local(), defining the expected
lists, and removed get_globals(). A variety of other minor changes abound,
principally in additional "FIXME" commentary.