removed visitors

D	src/ast/AST.java
M	src/ast/expressions/AddExpression.java
M	src/ast/expressions/AndExpression.java
M	src/ast/expressions/ConstExpression.java
M	src/ast/expressions/DivExpression.java
M	src/ast/expressions/EqualsExpression.java
M	src/ast/expressions/Expression.java
M	src/ast/expressions/MulExpression.java
M	src/ast/expressions/NegExpression.java
M	src/ast/expressions/NotExpression.java
M	src/ast/expressions/OrExpression.java
M	src/ast/expressions/SubExpression.java
M	src/ast/expressions/XorExpression.java
D	src/ast/visitors/EvalVisitor.java
D	src/ast/visitors/GraphvizVisitor.java
D	src/ast/visitors/SemanticVisitor.java
D	src/ast/visitors/StringVisitor.java
D	src/ast/visitors/Visitor.java
D	test/ast/visitors/AdvancedSemanticTests.java
D	test/ast/visitors/AdvancedTests.java