Replace current UpdateOfferView with Framework for new GridLayout (#944)

[Steffengreiner]

This PR aims to replace the current Stepper based implementation for the Update Offer View with a Grid based View as outlined here :

This will be done iteratively with seperate PRs:

• [x] Establish general structure of GridLayout and provide dummy views #944
• [ ] Implement Project Information Layout and wire ViewModel Logic necessary for ProjectInformationView #943
• [ ] Implement Project Manager Layout and wire ViewModel Logic necessary for ProjectManagerView #945
• [ ] Implement Update Customer Layout and wire ViewModel Logic necessary for CustomerView #945
• [ ] Implement SelectItems Layout and wire ViewModel Logic necessary for SelectItemsView
• [ ] Provide Costcalculation Logic from Items in SelectItems Layout
• [ ] Save and Cancel Offer Update Process with Reset Logic.