Include GUI in the setup.py file and fixes for GUI functionality

These settings are necessary for the functionality and inclusion of the GUI in the project, so it should be merged.

It includes one functionality change: Fixed icons so that they are loaded correctly when you are not in the correct folder and running the GUI.

b_asic/GUI/__init__.py

 """
 Better ASIC Toolbox GUI.
 TODO: More info.
-"""
\ No newline at end of file
+"""
+from b_asic.GUI.main_window import *
+from b_asic.GUI.about_window import *
+from b_asic.GUI.arrow import *
+from b_asic.GUI.drag_button import *
+from b_asic.GUI.gui_interface import *
+from b_asic.GUI.port_button import *
+from b_asic.GUI.properties_window import *
+from b_asic.GUI.select_sfg_window import *
+from b_asic.GUI.show_pc_window import *
+from b_asic.GUI.simulate_sfg_window import *
+from b_asic.GUI.utils import *