Added a solution level property called "TargetNsbVersion" to specify if the generated solution should target version 4.0 or 5.0
add support for getting nuget packages based on the target nsb version

Conflicts:
	src/ServiceMatrix.Automation/Model/Application.cs
bump up version to 2.1.1
exclude pre-release versions
Merge pull request #382 from Particular/fsimonazzi/backport-nuget-handling

Fsimonazzi/backport nuget handling
Merge branch 'hotfix-2.1.1'