WiP: Improvements regarding :hover on touch devices.

Also: No fading sidebar crap for touch devices.
Remove another "Off Franklin" leftover. Bye IE6!
Always show .reblog-links on touch-devices.
Fix default and .single-column #container widths.
Enable chromeless browsing on iOS (via the homescreen bookmark).

Maybe this should be bound to a "infinite scrolling enabled"-option later on?
More .no-touch:hover-related fixes.
Add basic support for HiDPI-avatar/-logo.

 * add additional custom Avatar image which will be used as HiDPI-image if present
 * no check yet if the device really is a HiDPI device

Along the way: Remove "apple-mobile-web-app-capable".