* Analyze nullability in script initializer

* C# 8 for scripts for now

* nullable context script test

* extra null check

* added possibility to set c# Language Version on ScriptOptions

* adjust tests

* added ScriptOptionsTests for C# lang version

* adapted tests after rebase

* code review changes

* fixed test names & resx CDATA

* changed the ScriptOptions.WithLanguageVersion error message text and moved it to ScriptingResources.resx

* Update CSharpScriptingResources.Designer.cs