Changed the signature of the Parser.parse interface: instead of ASTNode I let it return Form because this is the only allowed top level element in the language.
bug: typechecker - errormessage for And used '||' instead of '&&'.
Renamed Identity to Identifier.
Integrated the Declaration class with the Question class.
Split If into If and IfElse.
Made the constructor of TypecheckerVisitor private so it can't be instantiated from outside the class.
Changed the return type of the typechecker to a list of Messages instead of strings.
Removed unused methods and usings
Added type Void for ASTNodes which don't return a type, like a form or a question.
Added support for StoredExpression to the parser
Added support for StoredExpressions to the typechecker
Merge branch 'JessevanAssen-master' into JessevanAssen-clientUI
 - Fixed unit tests so they work again and incorporate new logic
 - Renamed Identity to Identifier
 - Removed the Declaration from the visitor
 - Added Void type to the visitors
 - Split If into If and IfElse
Made the constructor of KnockoutJSViewModelBuilderVisitor private so it can't be instantiated and the only way to call it is via the static method.
Added support for StoredExpressions in the KnockoutJSViewModelBuilderVisitor.