Documentation - Add description of BRepAlgoAPI_Algo::Shape()

In BRepBuilderAPI_MakeShape, the method Shape() checks if the shape is built and raises an exception if not.

In BRepAlgoAPI_Algo, the method Shape() is overriden. In BRepAlgoAPI_Algo::Shape(), the shape is returned as is (without any check).

The problem is that the description of BRepAlgoAPI_Algo::Shape() is missing. So, the description of the base method, BRepBuilderAPI_MakeShape::Shape(), is used in the documentation.

In the documentation page of BRepAlgoAPI_Algo (https://dev.opencascade.org/doc/refman/html/class_b_rep_algo_a_p_i___algo.html), the description of Shape() is : "Returns a shape built by the shape construction algorithm. Raises exception StdFail_NotDone if the shape was not built", which can lead to unsafe uses.

To fix this, I propose to add a description above BRepAlgoAPI_Algo::Shape() that clearly indicates that the returned shape is not checked.