gnu: Move contents of zip module into compression module.

gnu: Move contents of zip module into compression module.

* gnu/packages/zip.scm (zip, unzip, zziplib, perl-zip): Move to...
* gnu/packages/compression.scm: ...here.
* gnu/packages/zip.scm: Delete file.
* gnu/local.mk (GNU_SYSTEM_MODULES): Unregister deleted file.
* po/packages/POTFILES.in: Unregister deleted file.
* gnu/packages/{audio, avr, bioinformatics, busybox, cdrom, ci, compression,
docbook, documentation, fonts, fpga, game-development, games, gl, gnome,
gnuzilla, graphics, guile, haskell, image, java, kodi, ldc, libreoffice,
markup, maths, mc, monitoring, music, php, pretty-print, python, scheme,
smalltalk, statistics, synergy, tex, textutils, video, web-browsers, xml,
zip}.scm, guix/build-system/{ant, font}.scm, guix/{download, packages}.scm:
Adapt module import.