Enhancement - #307 show command

- introduced new show command to display configuration settings
- config command is used to just set config values
- modified documentation
- modified some unit tests calling 'task config' to 'task show'

src/tests/color.deprecated.t

@@ -41,7 +41,7 @@ if (open my $fh, '>', 'color.rc')
 }
 
 # Test the add command.
-my $output = qx{../task rc:color.rc config};
+my $output = qx{../task rc:color.rc show};
 like   ($output, qr/that use deprecated underscores/ms,  'Deprecated color detected');
 
 # Cleanup.