Fix default layout path

[QuasiStellar]

In #1421 DialogicDefaultLayout (formerly DialogicDefaultScene) was moved and renamed, however paths pointing to its location were not updated, because GDScript is a very good language and refactoring code written in it is always a pleasure.

There are some occasional formatting fixes to dilute the atmosphere of inevitable hardcoded doom.

[Jowan-Spooner]

Thanks for this PR.
However, we can now use DialogicUtil.get_default_layout() to get this path. The methods in settings general seem like they are not needed anymore.

[QuasiStellar]

Updated and tested with the same usecase.

[Jowan-Spooner]

Thanks!