[nextgen/cardstack] add slot support to components

- migrate existing code to slots
- add interactiveComponent.activeColor to overwrite the default "selected" button style
- improve handling of cached components

commands/message/search/news.js

@@ -78,7 +78,6 @@ module.exports = {
             type: InteractiveComponentTypes.BUTTON,
             label: "Full Coverage",
             icon: "button_full_coverage",
-            inline: true,
             visible: (pg) => {
               return (pg.getState("full_coverage_key") !== null)
             },