Fix the brand/cpu_string reversal.

Before this commit, the two were reversed ("cpu_string" had the brand, e.g. "AuthenticAMD"; and "brand_string" had the CPU type, e.g. "AMD Phenom II X4 925").
Fixes to the About dialog & add the SystemInfo dialog.

Also fix the build on Mac OS X.
Fixes from @comex to add the app bundle and icon on Mac.
Merge pull request #1388 from waddlesplash/dolphin-qt

DolphinQt: About dialog fixes, SystemInfo dialog