Modify template to support new app structure

[TheTechArch]

We need to create a new App template that will be the basis of all apps created in Altinn Studio going forward.

The goal is to get a application that can be run and debuged locally.

Location

• Locations for the App template should be under src/Altinn.Apps/AppTemplates/AspNet

Name

• The Name of the project should be App
• The namespace should be Altinn.Apps.App (Org and app should be set when app is created)
• The nuget namespaces should be Altinn.Apps.App.Controllers for controllers
• TODO Define namespaces for other common code put in nuget.

Structure

The basis template will be a ASP.Net Web Core 3.0 application. It will contains only the minimum files needed

• Startup.cs and program, CS
• Project file

Common functionality like controllers, (for standard API), process engine, PEP, used by the MVC will be put in nuget packages. #2803 decidew how

Services

• The app depends on serveral services

App logic

Tasks

• [x] Create new Template based on ASP.Net Web Api template
• [x] Create Nuget package with the controllers
• [x] Create Nuget package with service interfaces and
• [x] Create Nuget package with other functionality like pep
• [x] Define where static files like the react application should be put.
• [x] Define where files like XACML, BPMN should be put in the structure

[TheTechArch]

Based on decision in #2507 we need to modify the App template.

• Extract code that can be part of nuget

[TheTechArch]

This is completed. Handling issues as bugs. (if any)