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

FlatCAMWorker.py

@@ -1,6 +1,4 @@
 from PyQt4 import QtCore
-#import FlatCAMApp
-
 
 class Worker(QtCore.QObject):
     """
@@ -8,12 +6,33 @@ class Worker(QtCore.QObject):
     in a single independent thread.
     """
 
+    # avoid multiple tests  for debug availability
+    pydef_failed = False
+
     def __init__(self, app, name=None):
         super(Worker, self).__init__()
         self.app = app
         self.name = name
 
+    def allow_debug(self):
+        """
+         allow debuging/breakpoints in this threads
+         should work from PyCharm and PyDev
+        :return:
+        """
+
+        if not self.pydef_failed:
+            try:
+                import pydevd
+                pydevd.settrace(suspend=False, trace_only_current_thread=True)
+            except ImportError:
+                pass
+
     def run(self):
+
+        # allow  debuging/breakpoints in this threads
+        #pydevd.settrace(suspend=False, trace_only_current_thread=True)
+
         # FlatCAMApp.App.log.debug("Worker Started!")
         self.app.log.debug("Worker Started!")
 
@@ -21,9 +40,12 @@ class Worker(QtCore.QObject):
         self.app.worker_task.connect(self.do_worker_task)
 
     def do_worker_task(self, task):
+
         # FlatCAMApp.App.log.debug("Running task: %s" % str(task))
         self.app.log.debug("Running task: %s" % str(task))
 
+        self.allow_debug()
+
         # 'worker_name' property of task allows to target
         # specific worker.
         if 'worker_name' in task and task['worker_name'] == self.name:
@@ -35,4 +57,4 @@ class Worker(QtCore.QObject):
             return
 
         # FlatCAMApp.App.log.debug("Task ignored.")
-        self.app.log.debug("Task ignored.")
+        self.app.log.debug("Task ignored.")