added namespace class for namespaces of declarations
Fill namespaces with classes, fields and methods
added ref attributes to specific ast nodes
More work on semantisanalyer, Definition to interface
Merge branch 'nameanalysis'

Conflicts:
	mjcompiler-parser/src/main/java/edu/kit/pp/mjcompiler/parser/ast/ClassDeclaration.java
	mjcompiler-parser/src/main/java/edu/kit/pp/mjcompiler/parser/ast/FieldAccessExpression.java
	mjcompiler-parser/src/main/java/edu/kit/pp/mjcompiler/parser/ast/IdentifierExpression.java