Add refresh time counter

**The issue:**
When looking at the status viewer, the viewer doesn't know that it refreshes itself automatically. They might want to know when the server status was last refreshed.
**PR Breakdown:**
This PR solves that issue by adding a little refresh counter on the bottom right of the page, to indicate when the data was last refreshed. It resets that counter every time the data is updated.

It does that by adding additional HTML to `index.html` for the refresh counter and also adding a new timer function to `populate.js`, called `increaseTime()`. What the function essentially does is, it increases the second counter by one. That function gets called on a timer every second. The PR also adds a line to `populate()` to reset the counter to 0.

It also does show the grammatically correct version of the refresh time sentence, by adding and removing the "s" at the end of `seconds`.

The code does also work perfectly if connection to the status server is lost, it increases the time and resets it once the connection is re-established, as expected.

**Examples:**
`Last refreshed 0 seconds ago.`
`Last refreshed 1 second ago.` (Using "a" instead on "1" would require additional logic and is not that necessary in my opionion)
`Last refreshed 12 seconds ago.`

A live example can be seen at http://www.minotopia.me/status/.

Thanks!