registerurl, unregisterurl: Added --remote option

This serves two purposes. --remote=web bypasses other special remotes that
claim the url, same as addurl --raw. And, specifying some other remote
allows making sure that an url is claimed by the remote you expect,
which makes then using setpresentkey not be fragile.

Sponsored-By: the NIH-funded NICEMAN (ReproNim TR&D3) project

Command/Import.hs

@@ -75,7 +75,7 @@ data ImportOptions
 optParser :: CmdParamsDesc -> Parser ImportOptions
 optParser desc = do
 	ps <- cmdParams desc
-	mfromremote <- optional $ parseRemoteOption <$> parseFromOption
+	mfromremote <- optional $ mkParseRemoteOption <$> parseFromOption
 	content <- invertableSwitch "content" True
 		( help "do not get contents of imported files"
 		)