Support for reading registry keys' values

It would be a huge change, because when one is using custom install folders, CCleaner won't clean them. A good example is Steam, right now CCleaner checks for %ProgramFiles%\Steam\Steam.exe only, but it should read HKEY_CURRENT_USER\Software\Valve\Steam\SteamPath value. Supporting this for winapp2 is also a must, let's say something like this ReadValue1=HKEY_CURRENT_USER\Software\Valve\Steam\SteamPath and then storing that value in %ReadValue1% etc.