FIX: WebFactory failed to initialize on Windows

This is a trivial fix for a problem starting betterFORM on Windows. 

I ran into the problem because the current development eXist failed to start on a Windows system.

The unit test demonstrates the problem, but only when executed on a Windows machine: The resolvePath is platform-specific, so it may contain backslashes instead of slashes as path separators, leading to an StringIndexOutOfBoundsException in the unpatched version.