Add ability to change the modifiers for the C# and Java
interface generated when using the %interface macros.
For C# use the 'csinterfacemodifiers' typemap.
For Java use the 'javainterfacemodifiers' typemap.
For example:
%typemap(csinterfacemodifiers) X "internal interface"
Closes#1874
Add Java test for checking expected base and interfaces are generated (to be expanded further)
In the example, E was previously implementing IA, IB, IC. Now it doesn't implement any.
C# virtual/override still to be fixed for this test case