debuild: Revert to compat level 7, level 9 breaks various external builds when executed in a chroot environment.

debuild update: update to nw.js 0.15.4, remove DejaVu font from package for which we have a dependency anyway.

port agraef's commit from Pd-l2ork: debuild: remove obsolete preinst and postrm scripts. commit a1424f03364e5cbb79a19ee4142c6b4c101f597c

port agraef's commit from Pd-l2ork: debuild: more permission fixes. commit 7a1dd816b0fcbb42f733e7e715d3323d15608d33

port agraef's commit from Pd-l2ork: debuild: sanitize file permissions. commit 22edd363ff166125578cf1465a297c417c4e3665

port agraef's commit from Pd-l2ork: Adjust debuild so that it uses 'tar_em_up.sh -B -n' to do the staging. commit 835fa21ca36b5987a4bde01c7595293ff4c09abd

port from agraef's commit in Pd-l2ork: debuild: Add arduino folder. commit e12842b2009e7d44eb41fb46ef47f0cd9f35f840

port agraef's commit from Pd-l2ork: debuild: Add short sha to Debian package version for easier identification. commit a1c6862d5324eb014b573f6acc9ac668979d4c4f

port 79acee0a55fc5941685401e4c26c1ff741a10c62 from Pd-l2ork: Update debuild after wiringPi is now a submodule.

port 18d1c2a7a1794c7f63caff35cfc6c2e53e93e3a2 from Pd-l2ork: debuild: Auto-detect all submodules in the package