Allow the user to use custom path to fxml files

[manuel-mauky]

Using convention over configuration the fxml file has to be in the same package as the CodeBehind class. If this isn't working for a user we should provide a way to configure a custom path to the fxml file.

See this example:

package de.mycompany.myapp.MyView

@FxmlPath("/de/otherpath/OtherFilename.fxml")
public class MyView implements FxmlView<MyViewModel> {
}

[manuel-mauky]

reference #262

[rguillens]

I've implemented an initial approach to support this feature, check my PR.

[manuel-mauky]

This feature is implemented but still needs documentation in the wiki. For this reason I'm keeping this issue open for now.