Cleanup

[baseTwo]

TODO's. (Some items were done and have PR's assigned to them, but after some major merges, they need to be done again)

• [ ] Merge LibraryExpressionBuillder with ExpressionBuilder
• [ ] Pick more meaningful names for LibrarySet-, Library- and ExpressionBuilder. The term Expression is very overloaded, should perhaps refer to Definitions instead, since that is what is being build See PR comment
• [ ] Match namespace names to their folders
• [ ] Match class names to their files
• [ ] Correct usage of access modifiers. (private, protected, public, etc)
• [ ] Seal classes that are not going to be subclassed
• [ ] Small code cleanup comment in PR #418
• [x] Remove unused HL7 CQL files in CoreTests
• [x] Split *ExpressionBuilder/Context classes into separate files (PR #345)
• [ ] Remove all trailing whitespace (PR #345, #356)
• [ ] Refactor code to use collection initializer e.g. (PR #301)
  • List<int> list = [];, int[] arr = [1];
  • [] over Types.Empty or Array.Empty<T>() etc.
  • new string([..charList]) over new string(charList.ToArray())
  • [..arr1, ..arr2] over arr1.Concat(arr2).ToArray()

[baseTwo]

Since two big branches cql-to-elm and scopes have been merged into into develop-2.0, the sub tasks are re-opened