Develop integration 2019 w15

Integration Branch for develop: 2019 week 15

The following Merge Requests are included:

• MR 553: L2-nFAPI-simulator improvements and nFAPI code clean-up
• MR 554: Fixes on MAC scheduler
• MR 558: T: minor fix: ensure printing is inside the widget
• MR 559: UE T Tracer: bug fixes
• MR 561: Adding OAI UE + USRP test scenarios
• MR 567: Adding F1 - CU/DU test scenarios