fix --from overriding annex-ignore

Make git-annex get/copy/move --from foo override configuration of
remote.foo.annex-ignore, as documented.

This already worked for remotes supporting hasKeyCheap. For others though,
git-annex copy --from foo would silently not do anything, while
git-annex copy --to foo would use the annex-ignored remote.

Also improved the annex-ignore docs, to reflect that `git-annex get`
without --from will skip using annex-ignored remotes, for example.

Sponsored-by: Dartmouth College's DANDI project

Command/CheckPresentKey.hs

@@ -51,7 +51,7 @@ check :: String -> Maybe Remote -> Annex Result
 check ks mr = case mr of
 	Just r -> go Nothing [r]
 	Nothing -> do
-		mostlikely <- Remote.keyPossibilities k
+		mostlikely <- Remote.keyPossibilities (Remote.IncludeIgnored False) k
 		otherremotes <- flip Remote.remotesWithoutUUID 
 			(map Remote.uuid mostlikely)
 			<$> remoteList