Fix old hack on waitlist + personal trips queryset

Due to frustration with building a queryset from related objects, a
simple list was used on personal trips and waitlisted trips. Fix the
GET methods on both views so that a queryset of `Trip` models (with the
appropriate annotations and prefetching) is returned.
Responsive tables, mobile optimizations

Display only needed columns in desktop view, prevent wrapping from
distorting short fields, and use FooTable to make tables display cleanly
on mobile devices and other small screens.

Change the main menu for easier use on mobile devices (where clicking
and hovering are sometimes difficult to distinguish).