Metric Visualization Enhancements

[simianhacker]

The original stats panel allowed the user to add some formatting to the metric value. It would be awesome if we could get the following:

• Add an option to change the font size to the visualization options
• Add an option to add a custom label
• Add an option for formatting the number (45494 becomes 45,494)
• Add an option for formatting the number as money (45494 becomes $45,494 or 45,494€ - should have a pull down for different available formats)
• Center the value in the container using flexbox (center vertically and horizontally)

[lukasolson]

Custom labels/formatting should fall under #1543. But font size and flexbox are separate and valid.