Dashboard Cards Implementation

[bdeanindy]

Hey @robinwhitmore can an app have more than one dashboard_card?

I didn't see in the dashboard card documentation an explicit statement regarding if there is a fixed or maximum number of dashboard cards which an app can make available.

While I was considering the purpose of dashboard cards, my mind considered arguments for both sides and I wanted your input:

• An app should only expose a single dashboard card, because they are installed automatically when a user installs an app. A single card could have multiple groups or use external settings for very complex and informative dashboard cards, so a single card makes sense to enforce.
• An app could have multiple dashboard cards which it installs as a set of smaller, single-purpose management and reporting consoles for complex apps.

I figured I would ask the question, and then we can adjust/improve either this repository or the documentation accordingly.