Proper Debian packaging

For now we use 3.0 (native) which isn't exactly correct.

• Ship service file in make-pgp-clean-room (https://salsa.debian.org/tookmund-guest/make-pgp-clean-room/commit/487a0df0cea4f8836a61a1fe9e9ad4e783bced49 and https://salsa.debian.org/tookmund-guest/pgpcr/commit/b80b57c11b71d883e40210c406def242c889ee0f)
• Write proper descriptions for the binary packages
• Separate proper Debian packaging into its own repo branch (https://salsa.debian.org/tookmund-guest/pgpcr/tree/debian/master)
• Switch to 3.0 (quilt) https://salsa.debian.org/tookmund-guest/pgpcr/commit/88eeba2ba446255017c8f037147fe82c4793b0ce
• Stable release
• Upload package to mentors.d.o
• File RFS
• Package sponsored