Visual Studio 2019 Support

This PR provides a VS2019 compatible version of the VS Start page. #41

[x] Create logic for patching the Quick Start Window
[x] Restructure the UI and inject BetterStartPage
[x] Port the File > Open Favourite Menu to VS 2019
[x] Avoid duplicate opening of start page in case startup is not set to "Empty environment"
[x] Fix dialog misplacement in case startup is not set to "Empty environment"
[x] Adopt VS 2019 Styles
[x] Fix UI disturbances (border caused by resizable window)
[x] Center Quick Start Menu on launch #
[x] New Large/Small Display Mode
[x] Clean warnings
[ ] Polishing on the dialogs
[ ] Rework code to also provide old VS support.

Danielku15 / BetterStartPage