…ectly

 - udev is an alias for systemd, so just use that
 - while technically not wrong, fiddling with installFlags as well as the
   installFlagsArray bash variable is a little ugly so instead we override the phase
 - substituteInPlace i/o sed as it's much easier to read
 - ozw_config wasn't being substituted correctly

 - systemd i/o udev
 - do not override /etc/openzwave location so we can set it from nixos
 - substituteInPlace i/o sed
 - do not adjust pkg_config_path. If openzwave had its .pc files under usr/lib,
 that should be fixed instead.