[csharp] Implement selectors to C# language

[szabototo89]

Implement new selectors (method, property, variable etc.) to C# language

Declarations

• [x] class
  • [x] abstract
  • [x] partial
  • [x] sealed
  • [x] public/private/protected/internal
• [x] struct
• [x] interface
• [x] enum
• [x] variable
• [x] method
  • [ ] partial methods
  • [ ] parameter list
• [x] property
  • [ ] getter
  • [ ] setter
• [x] field
• [ ] namespace

  Statements

• [ ] using statements
• [x] if
• [x] while loop
• [x] for loop
• [x] foreach loop
• [ ] do-while
• [x] using

  Expressions

• [x] typeof
• [x] nameof
• [ ] assignment expressions
• [ ] method call
• [ ] access expressions