Added matrix-getter to Dataset.

Added rma-function to preprocessing incorporated in AffyMatrix-importer.
Added PCAFunction to go_workflow for processing loaded affymatrix data.

system/dataset.py

@@ -160,6 +160,10 @@ class Dataset:
         """Returns dataset name"""
         return self._name
 
+    def get_matrix(self):
+        """Returns internal numeric matrix for dataset."""
+        return self._array
+
     def get_all_dims(self):
         """Returns all dimensions in project"""
         return self._all_dims