docs: various small documentation fixes

docs/framework/quantity_points.rst

@@ -3,13 +3,15 @@
 Quantity Points
 ===============
 
-A `quantity point` is an absolute quantity with respect to zero
+A quantity point is an absolute quantity with respect to zero
 (which represents some origin) and is represented in the library with a
 `quantity_point` class template.
 
 
-Quantity Point Construction
----------------------------
+.. _quantity-point-construction:
+
+Construction
+------------
 
 To create the quantity point object from a `quantity` we just have to pass
 the value to the `quantity_point` class template explicit constructor::