Fix FCHost multiprocess mode initialization

CefExecuteProcess needs the App reference otherwise initialization in multi-process mode doesn't work correctly, which results in persistence being broken. I debug in single-process mode so I hadn't noticed this was broken before the refactoring was merged.

I'm assuming the same is true on linux so I changed it there too (@ezsh?).

I also have some doubts about how well the App refactoring is going to work on Mac (since the single-executable/multiple-process model doesn't work on Mac at all...see https://bitbucket.org/chromiumembedded/cef/wiki/GeneralUsage#markdown-header-entry-point-function - "The single executable structure is supported on Windows and Linux but not on MacOS."). Guess we'll cross that bridge when we come to it.