Additional global field options about block-lab

[rheinardkorf]

Required does not work for "SelectControl" "CheckboxControl", "ToggleControl" and "RadioControl".

[rheinardkorf]

Required is a boolean: "required": true , false by default.
Default is supplied using "default": <value>.
Field instructions is called help in Gutenberg, so option is "help": "Some help"

[lukecarbis]

That's a good point. Default value may not always work, either. I think that these should all be implemented outside of the abstract class, for two reasons:

1. More flexibility for controls to choose which "defaults" they include
2. More flexibility for controls to put options in the right order