PyMathics fns and vars called w/o qualifying

Allow PyMathics functions and variabls to be called without qualifying
the PytMathics context.

With this, I thin last bit of work in to be done mathics is complete.

Author: rocky

mathics/builtin/assignment.py

@@ -1710,4 +1710,17 @@ def apply(self, module, evaluation):
         except PyMathicsLoadException as e:
             evaluation.message(self.get_name(), 'notmathicslib', module)
             return Symbol('$Failed')
+        else:
+            # Add PyMathics` to $ContextPath so that when user don't
+            # have to qualify PyMathics variables and functions, 
+            # as the those in teh module just loaded.
+
+            # Following the example of $ContextPath in the WL
+            # reference manual where PackletManager appears first in
+            # the list, it seems to be preferable to add this PyMathics
+            # at the beginning.
+            context_path = evaluation.definitions.get_context_path()
+            if "PyMathics`" not in context_path:
+                context_path.insert(0, "PyMathics`")
+            evaluation.definitions.set_context_path(context_path)
         return module