Frontpage overhaul & add daily generated statistics

[m-rtijn]

The current frontpage is getting really big because the product database has grown a lot.

Suggested changes:

1. Move the "currently discounted" to a separate page"
2. Generate daily statistics and show these on the front page

Daily statistics

1. Product count
2. Prices count
3. Offers count
4. Average/median offer age ("How long have we been tracking a product?")
5. Top most often discounted product (highest % of prices in db are labeled as "discount")
6. Top least often discounted products (might be boring)
7. Most volatile products (which product has the most changes in its price)
8. there are always more interesting statistics to show!