Resolves #343 GUI and Frame Refactor

Major rewrite of the GUI into a module and view form, also using a new Feed class. The frame and frameset data structures have also been rewritten to support memory pooling and response frames.

CMakeLists.txt

@@ -233,6 +233,7 @@ if (BUILD_GUI)
 	set(NANOGUI_BUILD_EXAMPLE OFF CACHE BOOL " " FORCE)
 	set(NANOGUI_BUILD_PYTHON  OFF CACHE BOOL " " FORCE)
 	set(NANOGUI_INSTALL       OFF CACHE BOOL " " FORCE)
+	set(NANOGUI_EIGEN_INCLUDE_DIR ${EIGEN_INCLUDE_DIR} CACHE STRING " " FORCE)
 
 	# Add the configurations from nanogui
 	add_subdirectory(ext/nanogui)