add option to not optimize (g)zips within other (g)zips

[landfillbaby]

like --disable-png and --disable-jpeg
don't extract a zip, optimize it, then recompress it within the main zip

[landfillbaby]

better yet, just a single flag to disable recursion when (g)zipping

[fhanau]

Starting with c5e9219, ZIP files will no longer be recursively optimized if the strict option is enabled. Note that recursive optimization of gzip files does not happen even outside of strict mode.