Make the default dashboard modular

[rdiaztushman]

Notes from Skype discussion:

1. search. i think there's already a ticket for it. Default view in the admin should be a search view? #38

2. realtime traffic feed (if f3-activity is installed)

3. tabs to see yesterday's traffic report, last 7 days, last month's, last 90 days

4. activity feed -- "User viewed X.", "User updated Y", "User carted Z" -- with ability to switch between site & admin activity

5. shop summary data (if shop is installed)

6. affiliates summary data (if affiliates is installed)

routes for the dashboard:

• /admin == the same content as /admin/dashboard/today
• /admin/dashboard/yesterday
• /admin/dashboard/last-7
• /admin/dashboard/last-30
• /admin/dashboard/last-90