install, install-builddep: Cleanup, bugfixes.
lpf: bugfix
pkgbuild: Don't allow scan bypassing pkgbuild.

Routing all code running as pkg-buil user means that we can
tighten up the sudo config.
scripts: Get rid of PKGBUILD_SUDO, trust lpf-pkgbuild.
kill-pgroup: Cleanup.
defs: Remove some over-engineered functions.
lpf-gui: Add a reset button.
README: update