update doxyfile to generate and include models/ documentaiton

Doxyfile

@@ -829,7 +829,7 @@ WARN_LOGFILE           =
 # spaces. See also FILE_PATTERNS and EXTENSION_MAPPING
 # Note: If this tag is empty the current directory is searched.
 
-INPUT                  = include/ src/ test/core/ test/geojson/ test/models/ README.md CHANGELOG.md doc/ INSTALL.md CONTRIBUTING.md TERMS.md test/README.md
+INPUT                  = include/ src/ models/ test/core/ test/geojson/ test/models/ README.md CHANGELOG.md doc/ INSTALL.md CONTRIBUTING.md TERMS.md test/README.md
 
 # This tag can be used to specify the character encoding of the source files
 # that doxygen parses. Internally doxygen uses the UTF-8 encoding. Doxygen uses
@@ -2152,7 +2152,7 @@ SEARCH_INCLUDES        = YES
 # preprocessor.
 # This tag requires that the tag SEARCH_INCLUDES is set to YES.
 
-INCLUDE_PATH           = include/
+INCLUDE_PATH           = include/ models/
 
 # You can use the INCLUDE_FILE_PATTERNS tag to specify one or more wildcard
 # patterns (like *.h and *.hpp) to filter out the header-files in the