Limitscolor widget colors and support no label

[jmthomas]

The limitscolor widget uses default css values for green, yellow, and red instead of the cosmos defined colors present in limitsbar. These should be consistent.

The last parameter indicates true to support a full TGT PKT ITEM label but is supposed to NOT display the label at all when passed nil (or none). This is currently broken.

Update the DEMO to use NIL / NONE as the last parameter and show how to use LABEL to add a custom label.