add expression project

Tutorials/expression-project/.gitignore

Tutorials/expression-project/bonus-solution/.classpath

Tutorials/expression-project/bonus-solution/.project

...als/expression-project/bonus-solution/.vscode/launch.json

...expression-project/bonus-solution/src/ast/ASTFactory.java

...t/bonus-solution/src/ast/expressions/ConstExpression.java

...roject/bonus-solution/src/ast/expressions/Expression.java

...-project/bonus-solution/src/ast/expressions/Operator.java

...us-solution/src/ast/expressions/binary/AddExpression.java

...us-solution/src/ast/expressions/binary/AndExpression.java

...solution/src/ast/expressions/binary/BinaryExpression.java

...us-solution/src/ast/expressions/binary/DivExpression.java

...solution/src/ast/expressions/binary/EqualsExpression.java

...us-solution/src/ast/expressions/binary/MulExpression.java

...nus-solution/src/ast/expressions/binary/OrExpression.java

...us-solution/src/ast/expressions/binary/SubExpression.java

...us-solution/src/ast/expressions/binary/XorExpression.java

...nus-solution/src/ast/expressions/unary/NegExpression.java

...nus-solution/src/ast/expressions/unary/NotExpression.java

...s-solution/src/ast/expressions/unary/UnaryExpression.java