#322 Option to require variable declaration

[Dave]

The Dr Java interactions window allows one to omit the variable type declaration, and it infers the type from the variable's initial assignment statement. For those using Dr Java to teach, it would be useful to have a preference setting that requires the variable's type to be declared explicitly in the interactions window. Otherwise, students get used to omitting the variable type in the interactions window, and then are left to wonder what the error message in the declarations window is all about, which is confusing because the code causing the error works in the interactions window.