Resolve "Simulate SFG in GUI"

Implemented the GUI handling of simulation of an SFG, also fixed some other stuff like new selection handling (any bugs are features), naming sfg, etc. Closes #88 (closed)

b_asic/GUI/arrow.py

@@ -5,7 +5,7 @@ QGraphicsLineItem, QGraphicsWidget
 from PySide2.QtCore import Qt, QSize, QLineF, QPoint, QRectF
 from PySide2.QtGui import QIcon, QFont, QPainter, QPen
 
-from b_asic import Signal 
+from b_asic import Signal
 
 class Arrow(QGraphicsLineItem):
 
@@ -25,6 +25,8 @@ class Arrow(QGraphicsLineItem):
         menu.exec_(self.cursor().pos())
 
     def remove(self):
+        self.signal.remove_destination()
+        self.signal.remove_source()
         self._window.scene.removeItem(self)
         self._window.signalList.remove(self)