Immediately error when a secure option (e.g. repo1-s3-key) is passed on the command line.

Since pgBackRest would not pass secure options on to sub-processes an obscure error was thrown. The new error is much clearer and provides hints about how to fix the problem.

Update command documentation to omit secure options that cannot be specified on the command-line.

Reported by Brad Nicholson.

doc/lib/BackRestDoc/Common/DocConfig.pm

@@ -700,6 +700,9 @@ sub helpCommandDocGet
 
             foreach my $strOption (sort(keys(%{$$oCommandHash{&CONFIG_HELP_OPTION}})))
             {
+                # Skip secure options that can't be defined on the command line
+                next if ($rhConfigDefine->{$strOption}{&CFGDEF_SECURE});
+
                 my ($oOption, $strCategory) = helpCommandDocGetOptionFind($oConfigHash, $oOptionDefine, $strCommand, $strOption);
 
                 $$oCategory{$strCategory}{$strOption} = $oOption;