libpt2, a universal library and QML plugin to deal with public transportation

libpt2 roots from libpublictransportation, an attempt to provide a way to merge
public transportation related informations into one library, in order for an 
unique application to manage multiple public transportation related information.

libpt2 is a small rewrite, that borrows a lot from libpublictransportation. It
is now written in Qt 5, and aims at being integrated into Nemo based products
(Nemo mobile and Sailfish OS).