UI improvements for data display in the Cache tab

[miko-ck]

2 little requests:

1. I'd like to make the text size smaller to make better use of the screen space
2. I'd like to be able to copy, or at least select the displayed data.

Here's a screenshot that shows both problems. You can see the context menu that appears when I right-click on an object, which is just the common menu that appears on any other text.

If you'd reuse the DevTools component that displays JSON values in console, it'd solve both these problems. It uses the same font as everything else, and has a context menu with some extra options.