exit upon escape on main menu
add basic SP load menu, remove qml debug statements for ESC presses
rm unnecessary cmake stuff (librocket especially, that's no longer used)
attempt to create a 3.1 context explicitly

unfortunately it segfaults deep in qt regardless of what i do
loadworld menu implemented (even though it's not filled with anything good)
make a couple slots for qml -> Client(cpp) so e.g. create world->play works