Updated CFW FAQ with the latest details. Corrected a detail about the relationship between arcade `.zfb` files and the `.zip` files they point to (thanks `.ericgoldstein`!). Added a note to the Firmware section about the official firmware update process wiping the microSD card, and a note to the Save States section about how to back up game saves (thanks for the suggestion @uli42! Closes#10). Added a simple firmware version checking tool, so that folks don't have to use the boot logo changer to check (which always seemed clunky to me). Added a link to `dteyn`'s silent sounds pack. Fixed some small typos.
