Seal InputBoxType
Limit Chooseable options to string, double, boolean, logolist
Textbox escapes and unescapes display string on parsing and writing
Allows chooser to have a default value of a string containing "//"
Represent widget constraints as data objects
Move ConstraintSpecification trait out of Widget.scala
Merge pull request #16 from NetLogo/wip-typed-chooser

InputBox and Chooser should restrict type rather than use AnyRef