Extract compute shape functions for arbitrary points
Follow-up of !3063 (merged).
In several processes computation of the shape function in special/arbitrary points is required. The initShapeMatrices() method accepts an integration method and computes the shape matrices at the integration points.
The split method accepts a container with points for which the shape matrices are computed.
Changes mainly consist of:
- extracting computeShapeMatrices() method from initShapeMatrices()
- and code deduplication.
Review commit-wise.