New files for Network calculus

Makefile

src/Main.java

src/nc/NCElement.java

src/nc/NCEquipment.java

src/nc/NCLink.java

src/nc/NCLinkedElement.java

src/nc/NCPath.java

src/nc/NCStructure.java

src/nc/NCSwitch.java

src/nc/NCTraffic.java

src/ui/MainGUI.java