Ensure telepathy-logger-qt can be used with Qt5

Merges cmake scripts back from telepathy-qt, which is where they seem to
have been forked from.
Drops Qt4 cmake code-paths
Renames everything called Qt4 to Qt, so we don't have this weird problem
again.
Drops debugging macros because they were somewhat colliding with qDebug
being a macro as well. QDebug provides all needed features currently anyway.