- extend PaymentServer with setOptionsModel() and rework initNetManager()
to make use of that
- fix all other places in the code to use display unit from options and no
hard-coded unit
- try to enforce the same style to all Qt related files
- remove unneeded includes from the files
- add missing Q_OBJECT, QT_BEGIN_NAMESPACE / QT_END_NAMESPACE
- prepares for a pull-req to include Qt5 compatibility