message: Removed =default c'tor workaround for VS2015 in PcaModel
  Hopefully this is not an issue anymore.
diff: @@ -55,7 +55,7 @@ cv::Mat unnormalise_pca_basis(cv::Mat normalised_basis, cv::Mat eigenvalues);
  class PcaModel
  {
  public:
  - PcaModel() {}; // workaround for a VS2015 RC bug. Change to '=default' in RTM.
  + PcaModel() = default;
  /**
  * Construct a PCA model from given mean, normalised PCA basis, eigenvalues
  