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

FlatCAM.py

@@ -1,5 +1,6 @@
 import sys
 from PyQt4 import QtGui
+from PyQt4 import QtCore
 from FlatCAMApp import App
 
 def debug_trace():
@@ -10,6 +11,10 @@ def debug_trace():
     #set_trace()
 
 debug_trace()
+
+# all X11 calling should  be thread safe  otherwise we have  strenght issues
+QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_X11InitThreads)
+
 app = QtGui.QApplication(sys.argv)
 fc = App()
 sys.exit(app.exec_())