Adapt the ScalarFieldSample instances of single runs to the Pointlist of the StressFacade

[jmborr]

A single runs, represented by a StrainFieldSingle object, has an unstacked PointList attribute, lacking some of the sample points in the stacked PointList. When requesting data from a single run, the data has to be adapted to the stacked PointList

To-do:

• retrieve the data from the single run
• check if the point list from the single run coincides with the stacked point list
• if different, stack both point list in order to adapt the single point list ot the stacked point list
• fill the missing values with NaN