Added a separate doxygen file to document the namespaces

This makes all free functions show up in the generated documentation.

doc/Doxyfile.in

@@ -2,6 +2,7 @@ PROJECT_NAME           = "@CMAKE_PROJECT_NAME@"
 PROJECT_NUMBER         = @eos_VERSION_MAJOR@.@eos_VERSION_MINOR@.@eos_VERSION_PATCH@
 STRIP_FROM_PATH        = @PROJECT_SOURCE_DIR@
 INPUT                  = @PROJECT_SOURCE_DIR@/README.md \
+                         @PROJECT_SOURCE_DIR@/doc/namespaces.doxygen \
                          @PROJECT_SOURCE_DIR@/include
 RECURSIVE              = YES
 EXCLUDE_PATTERNS       = */detail/*

doc/namespaces.doxygen

+/**
+ * @namespace eos
+ * @brief Namespace containing all of eos's 3D model fitting functionality.
+ */
+
+/**
+ * @namespace eos::core
+ * @brief Essential functions and classes to work with 3D face models and landmarks.
+ */
+
+/**
+ * @namespace eos::fitting
+ * @brief Pose and shape fitting of a 3D Morphable Model.
+ */
+
+/**
+ * @namespace eos::morphablemodel
+ * @brief Functionality to represent a Morphable Model, containing it's PCA models and loading functions.
+ */
+
+/**
+ * @namespace eos::render
+ * @brief 3D mesh and texture extraction functionality.
+ */