Adds unary operators to the AstBuilder.
Merge branch 'Perenthesis' into UnaryOperators
Switches Evalution project type to ClassLibrary.
Adds TestUnaryOperatorAndParenthesis unit test
Merge branch 'develop' into UnaryOperators
Implements Unary expressions (- and +).

! is not implemented yet.
Merge branch 'UnaryOperators' into develop
Merge branch 'develop'