Added dwell (G4) post processing option to gcode.

ObjectUI.py

@@ -163,7 +163,9 @@ class CNCObjectUI(ObjectUI):
         )
         self.custom_box.addWidget(self.updateplot_button)
 
+        ##################
         ## Export G-Code
+        ##################
         self.export_gcode_label = QtGui.QLabel("<b>Export G-Code:</b>")
         self.export_gcode_label.setToolTip(
             "Export and save G-Code to\n"
@@ -194,6 +196,26 @@ class CNCObjectUI(ObjectUI):
         self.append_text = FCTextArea()
         self.custom_box.addWidget(self.append_text)
 
+        # Dwell
+        grid1 = QtGui.QGridLayout()
+        self.custom_box.addLayout(grid1)
+
+        dwelllabel = QtGui.QLabel('Dwell:')
+        dwelllabel.setToolTip(
+            "Pause to allow the spindle to reach its\n"
+            "speed before cutting."
+        )
+        dwelltime = QtGui.QLabel('Duration [sec.]:')
+        dwelltime.setToolTip(
+            "Number of second to dwell."
+        )
+        self.dwell_cb = FCCheckBox()
+        self.dwelltime_entry = FCEntry()
+        grid1.addWidget(dwelllabel, 0, 0)
+        grid1.addWidget(self.dwell_cb, 0, 1)
+        grid1.addWidget(dwelltime, 1, 0)
+        grid1.addWidget(self.dwelltime_entry, 1, 1)
+
         # GO Button
         self.export_gcode_button = QtGui.QPushButton('Export G-Code')
         self.export_gcode_button.setToolTip(