Qt5 build setup, remove qmlog dependency, simplify header includes

OBS packages for libiodata and libiodata-qt5: https://build.merproject.org/project/packages?project=home%3Apgerdt%3Abranches%3Anemo%3Adevel%3Amw

This pull request includes changes from Matthew Vogts pull request https://github.com/nemomobile/libiodata/pull/1.