Ability to modify by adding/removing; formatting

Changed the way the output was formatted to make the MainMenu "more
responsible for itself." (Though it should still look the same, the
MainMenu class now takes more care of inserting newlines to separate
blocks of output more logically.) More importantly, added the ability to
modify Surveys and Tests by adding more questions to them and removing
questions from them. (In Test, removing a question will also remove the
correctResponse).