(#541) Added feature for export of well log plot curves to a LAS file

Did some refactoring/improvements by introducing new class
RigWellLogCurveData.

ApplicationCode/ReservoirDataModel/RigWellLogFile.h

@@ -30,6 +30,7 @@ namespace NRLib
     class Well;
 }
 
+class RimWellLogPlotCurve;
 
 //==================================================================================================
 /// 
@@ -51,6 +52,8 @@ public:
     QString depthUnit() const;
     QString wellLogChannelUnit(const QString& wellLogChannelName) const;
 
+    static bool exportToLasFile(const RimWellLogPlotCurve* curve, const QString& fileName);
+
 private:
     void close();