Create print layout

[Danielku15]

alphaTab currently only has:

1. a vertical (historically named 'page') which does dynamic scaling based on the available width
2. a horizontal layout

We started to add more explicit layouting information via SystemsLayoutMode.UseModelLayout.

To have first class support of rendering precise music sheets that as intended by MusicXML, Guitar Pro and Capella (and even can be printed) we should add a dedicated new layout Print (as 'page is already taken wrongly). The print layout would be a precise page layout with the page size defined in the stylesheet.

As system heights depend on the application (alphaTab in this case) the page fitting is always happening automatically. We then do a proper vertical stretching

https://guido.grame.fr/papers/kai_renz_diss.pdf has again some good chapters on that to have proper even spacing. To have a nice looking page the visible staves should be spread fairly evenly. But "evenly" means respecting additional spacing required y overflows and effect staves properly.