Servatrice win32 fixes

Misc fixes referencing #343. Target is being able to ship servatrice inside the windows package, and let users run it as a local server without the need of any configuration.
This method would become more readable if it was restructured as something like:

* construct list of locations to check
* foreach loop over list
* check if file exists, is file, can be read, opened without error
* on open error, abort server with qCritical message on the failure
* on open success, return