Initial PR to enable embedding images in Doxygen (#4491)

* Initial PR to enable embedding images in Doxygen

* Address review comments

doc/doxygen/Doxyfile.in

@@ -10,6 +10,8 @@ USE_MATHJAX      = YES
 
 GENERATE_XML     = YES
 
+IMAGE_PATH       = @CMAKE_SOURCE_DIR@/doc/doxygen/images/
+
 WARN_IF_UNDOCUMENTED = @DOXYGEN_WARN_IF_UNDOCUMENTED@
 QUIET                = @DOXYGEN_QUIET@
 

doc/doxygen/images/README.md

+Add any images required for Doxygen documentation in this folder.
+
+How to use the image in your documentation:
+1. Add the image to be displayed in your documentation to this folder say example.svg
+
+2. To use this image to display in your code say in code.hpp, following is an example
+/// This is the comment description and the line below displays the image
+/// \image html example.svg
+
+3. For more details http://www.doxygen.nl/manual/commands.html#cmdimage