reformat, organize and cleanup

src/root/EvalVisitor.java

src/root/Main.java

src/root/StringVisitor.java

src/root/ast/expressions/AddExpression.java

src/root/ast/expressions/AndExpression.java

src/root/ast/expressions/BNegExpression.java

src/root/ast/expressions/BinaryExpression.java

src/root/ast/expressions/ConstExpression.java

src/root/ast/expressions/DivExpression.java

src/root/ast/expressions/EqualsExpression.java

src/root/ast/expressions/Expression.java

src/root/ast/expressions/MulExpression.java

src/root/ast/expressions/NegExpression.java

src/root/ast/expressions/Operators.java

src/root/ast/expressions/OrExpression.java

src/root/ast/expressions/SubExpression.java

src/root/ast/expressions/UnaryExpression.java

src/root/ast/expressions/XorExpression.java

src/root/visitors/EvalVisitor.java

src/root/visitors/GraphvizVisitor.java