`extern SP_Circuit` decleration

[ecrinyildiz]

idk how to point out the problem but the decleration of extern SP_Circuit cirtuit in main.h causes a lot of trouble. we do MUST inject this variable into the GUI/SaveLoad via "main.h" inclusion. during the modularization process, i CANT seperate the gui folder with the apps folders(which is the application layer, it should depends the modules but not directly bonded with them). so it means gui module cant live standalone
suggestions:

• we can pass the variable into the gui manager.
• we can use singleton pattern to access the circuit
  im open to discuss any other alternative solutions

[ecrinyildiz]

we can introduce a brand new circuitManager class that keeps the extern SP_Circuit circuit as a unique or shared ptr then we can pass it anytime we need

[Batucan2601]

A singleton class might not cut it, since we do not know if Circuit is needed with more than one instances I guess ? Will think about it.