Fix wrong usage of `QObject` leading to warnings

Classes inheriting from `QObject` must use the `Q_OBJECT` macro. This was
not the case and thus causing warnings. Since the `QObject` base class was
not utilized here anyways except for `tr()` I simply removed the that
inheritance.

src/Conductor.cpp

@@ -315,7 +315,7 @@ void CConductor::reconnectMidi()
 {
     if (!validMidiOutput()) {
         QString midiInputName = m_settings->value("Midi/Input").toString();
-        if (midiInputName.startsWith(tr("None"))) {
+        if (midiInputName.startsWith(QCoreApplication::translate("CConductor", "None"))) {
             CChord::setPianoRange(PC_KEY_LOWEST_NOTE, PC_KEY_HIGHEST_NOTE);
         } else {
             CChord::setPianoRange(m_settings->value("Keyboard/LowestNote", 0).toInt(),

src/MidiDeviceBase.h

@@ -37,7 +37,7 @@
 
 #include "MidiEvent.h"
 
-class CMidiDeviceBase : public QObject
+class CMidiDeviceBase
 {
 public:
     virtual void init() = 0;

src/MidiDeviceFluidSynth.h

@@ -63,7 +63,7 @@ public:
 
     static QString getFluidInternalName()
     {
-        return QString(tr("Internal Sound") + " " + FLUID_NAME );
+        return QCoreApplication::translate("CMidiDeviceFluidSynth", "Internal Sound %1").arg(QString::fromUtf8(FLUID_NAME));
     }
 
 private: