Add item count to the stats page

[cyphun]

We want to be able to see how many items are associated with this stats page.

Acceptance criteria

• This should have it's own section titled <h3>Total items</h3>
• Then it should have a <p> that says something along the lines of "This site|community|collection|etc has 1,300 items" -- depending on the stats page they are looking at
• The items count section is not shown on an individual stats page
• Place this section at the bottom of the page under "Top 10 items with the most file downloads"