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.h

@@ -53,7 +53,7 @@ namespace BlackMisc
         CMessageBase() {}
 
         //! Construct a message with some specific category.
-        explicit CMessageBase(const CLogCategory &category) : m_categories( { category }) {}
+        explicit CMessageBase(const CLogCategory &category) : m_categories({ category }) {}
 
         //! Construct a message with some specific categories.
         explicit CMessageBase(const CLogCategoryList &categories) : m_categories(categories) {}