maliit-*-qt5: Adjust MKSPEC path
meta-framework-qt5: Cleanup packaging and enable dbus activation.

* Move pkgconfig files, headers and spec files into dev.
* Cleanup packaging rules
* Enable dbus activation to start maliit server on demand
maliit-plugins-qt5: Set MALIIT_PLUGINS_DATA_DIR to avoid path leakage from host

If not overriden here MALIIT_PLUGINS_DATA_DIR would point to some host
paths resulting in e.g. qml files not being found.