Update account menu to allow defining active link

[rpowis]

This allows the account menu items to be set as active.

• Only account menu, messages, and check progress can be set as active
• The account menu defaults to active if none are explicitly set

[nataliecarey]

OK, on our side this looks good, what's the likely impact on users? Dynamically/conditionally setting a field on an object inside an array is more complex. As these items all have names should we use something more like active: "accountHome"?

To be clear - I think this interface is great for our side of the contract but I'm wondering how easy people will find it to consume.