Migrate to .NET 6 / .NET Standard 2.0

[eXpl0it3r]

• [x] Check that CM are all on .NET Standard 2.0
• [x] Check dependency support for at least .netstandard2.0
  • [x] Create a table with the overview in the docs repo
• [x] Use Upgrade Assistant to upgrade the projects
  • [x] jobbr-cm-jobstorage
  • [x] jobbr-cm-artefactstorage
  • [x] jobbr-cm-execution
  • [x] jobbr-cm-management
  • [x] jobbr-cm-registration
  • [x] jobbr-runtime
  • [x] jobbr-execution-forked
  • [x] jobbr-server
  • [x] jobbr-storage-mssql
  • [x] jobbr-artefactstorage-filesystem
  • [x] #83
  • [x] demo
  • [x] jobbr-dashboard
• [x] Removing ILMerge / Fody / Costura.Fody
• [x] Define a new version scheme (which version goes together with which version)

[eXpl0it3r]

Moved RavenDB changes to #104

[eXpl0it3r]

Moved the InProcess update to #50, since it was never fully finalized

[eXpl0it3r]

Migration completed and released: https://github.com/jobbrIO/jobbr-server/releases/tag/v3.0.0