[docs] Update mainpage

doc/doxygen/mainpage.md

@@ -2,6 +2,7 @@
 
 > **Note:** This is the **%Cantera Developer API** documentation; for general
 > information on %Cantera, refer to [**cantera.org**](https://cantera.org).
+> The %Cantera source code is hosted on [GitHub](https://github.com/Cantera/cantera).
 
 Use sidebar or menu at the top to view detailed documentation of the code, or
 use the following shortcuts:
@@ -10,7 +11,7 @@ use the following shortcuts:
 * Index of [**Cantera C++ Classes**](classes.html)
 * \ref sec-yaml-documentation
 
-A topical overview is provided as follows:
+A topical overview of C++ modules is provided as follows:
 
 * \ref solnGroup (interface to %Cantera core objects)
 * \ref thermoprops (temperature, pressure, energy, ...)
@@ -23,5 +24,3 @@ A topical overview is provided as follows:
 For fundamental scientific theory used for the implementation of %Cantera, refer to the
 [Cantera Science Section](https://cantera.org/science/index.html) of the
 [Cantera Website](https://cantera.org).
-
-The %Cantera source code is hosted on [GitHub](https://github.com/Cantera/cantera).

interfaces/cython/cantera/_utils.pyx

@@ -174,7 +174,7 @@ cdef class AnyMap(dict):
     A key-value store representing objects defined in Cantera's YAML input format.
 
     Extends the capabilities of a normal `dict` object by providing functions for
-    converting values between different unit systems. See :ref:`sec-yaml-units` for
+    converting values between different unit systems. See YAML Format Reference for
     details on how units are handled in YAML input files.
     """
     def __cinit__(self, *args, **kwawrgs):