Deployed shadow build filenames must be converted to project filenames if available

When a qmake-based QML app is built as a shadow build, qml files are typically copied to the build directory. This creates a problem with the QML debugger: the user will see shadow build files when a breakpoint is hit, which is less than ideal.

Solution: In DebuggerPlugin::gotoLocation(), the shadow build filenames must be converted, or the method must be virtualized and reimplemented in QmlEngine.