merge new pull requests from FlatCAM->master

implement  executing of tasks  inside worker thread
cleanups, reimplement  Isolate/New/OpenGerber as OOP style Shell commands
disable edit  during shell execution,  show   some  progress
add ability for breakpoints in other threads and only if available
add X11 safe flag, not sure what happen on windows

FlatCAMShell.py

@@ -22,4 +22,4 @@ class FCShell(termwidget.TermWidget):
         return True
 
     def child_exec_command(self, text):
-        self._sysShell.exec_command(text)
+        self._sysShell.exec_command(text)