Status message fix, copy timestamp in assigmnet operator

* the timestamp of status message was not copied, so every time a status message was sorted or otherwise assigned the ts got lost or wrongly assigned.
* this meant the log messages were in wrong order, leading to very confusing results in the log screen or file.
* also added new timestamp formatter
* new function "BlackMisc::CVariant displayRole(const PQ &pq) const" which can be used if the PQ is already available

src/blackmisc/statusmessage.cpp

@@ -97,10 +97,12 @@ namespace BlackMisc
 
         QReadLocker readLock(&other.m_lock);
         auto handledBy = other.m_handledByObjects;
+        qint64 ts = other.m_timestampMSecsSinceEpoch;
         readLock.unlock(); // avoid deadlock
 
-        QWriteLocker writeLock(&this->m_lock);
+        QWriteLocker writeLock(&m_lock);
         m_handledByObjects = handledBy;
+        m_timestampMSecsSinceEpoch = ts;
         return *this;
     }