Lots of changes

So very many changes, including:
-Added vaguely style-guide-like semi-proper-ish XML documentation to
everything for marks and also the Visual Studio tag thing when
programming with the stuff.
-Re-named the Main form from frmMainMenu to frmMain because year 1 and 2
style guide gangsta yeee.
-Made the interface easier to read for old people by increasing the font
size all-around. lol.
-Added the Add Booking form and un-cluttered the Check-In form.
-Added a
possibly-semi-experimental-depending-on-whether-people-like-it-or-not
background thing for the Main form/MDI parent container. It's basically
a borderless form that always sits in the back and provides some
quick-access buttons to whatever the most common functions are and
stuff.
-Lots more little stuff that I can't think of because I'm the worst
documenter.