Prep work for graphics

*Indented the main loop block in Driver. For some reason this isn't
showing in the Git preview. Maybe my Eclipse settings are different.
*Fixed a bug in sort. Places of interest case was nested inside city
case.
*Added a method to ShowGraphic. There's a second type of bar graph
described in the assignment.
*All ShowGraphic methods currently just print to the console to ensure
proper program flow before implementing the graphs.
*Changes to getOutputPreference:
--Dialog now has (conditionally) a "Graphical Display" option, if it's
appropriate given prior selections.
--Added dataType argument, since the Graphical Display option needs to
know this.
--Graphical Display option works, but the methods it calls (from
ShowGraphic) aren't implemented.