Added separation between the wallet types on download page

It took me a minute to understand why blockchain.info's icon was on the "choose your wallet" page twice, and I also remember wondering whether it'd be clear to users that some downloads are not desktop applications. I only understood once I the text above the icons.

Since many people don't read the all the text on a page (especially a page leading to downloads), I think this visual hint, separating the different client types, makes it clearer that there is not only the choice of which wallet to use, but also different types of wallets.

Screenshot of change (to compare with bitcoin.org/en/choose-your-wallet): http://imgur.com/PcCqIEO