Ref T241, Ref T243, ITimestampWithOffsetObjectList

* there was already ITimestampWithOffsetBased for objects
* this creates the container version
* functions to add objects (parts/situations) and guarantee the sort order
* moved push_frontMaxElements to CSequence (not specific for timestamp lists)
* added in-place reverse

src/blackmisc/timestampbased.h

@@ -161,6 +161,9 @@ namespace BlackMisc
         //! Milliseconds to add to timestamp for interpolation
         qint64 getTimeOffsetMs() const { return m_timeOffsetMs; }
 
+        //! Having a valid offset time
+        bool hasOffsetTime() const;
+
         //! Offset with unit
         QString getTimeOffsetWithUnit() const;