adblock: release 4.5.6-1

adblock: release 4.5.6-1

- f_etag: strip CR in ETag header extraction (gsub(/[\r"]/,…)) — fixes empty-but-present etag
- f_etag: add feed_rm mode to drop a feed's etag entries; roll back the optimistically stored etag on failed downloads
- f_list/f_main: make restore-failure feed pruning subshell-safe via per-feed marker files
- f_jsnup: remove bogus trailing commas from the active_feeds array elements
- f_fetch: validate adb_fetchretry
- f_conf: ignore empty UCI option values so they don't override sane defaults
- f_report: add jclean() to strip control/quote/backslash from untrusted client/iface/domain fields
- LuCI: fix some cornercase issues
- update readme

Signed-off-by: Dirk Brenken <redacted>