- replaced the testing if instance of FlatCAMObj with testing the obj.kind attribute

- removed the import of the whole FlatCAMApp file only for the usage of GracefulException
- remove the import of FlatCAMApp and used alternate ways
- optimized the imports in some files
- moved the Bookmarksmanager and ToolDB classes into their own files
- solved some bugs that were not so visible in the Editors and HPGL parser
- split the FlatCAMObj file into multiple files located in the flatcamObjects folder and renamed the contained classes with names more suggestive
- updated the Google Translation for the German language

flatcamTools/ToolDblSided.py

@@ -191,7 +191,7 @@ class DblSidedTool(FlatCAMTool):
         # Add a reference
         self.add_point_button = QtWidgets.QPushButton(_("Add"))
         self.add_point_button.setToolTip(
-            _("Add the coordinates in format <b>(x, y)</b> through which the mirroring axis \n "
+            _("Add the coordinates in format <b>(x, y)</b> through which the mirroring axis\n "
               "selected in 'MIRROR AXIS' pass.\n"
               "The (x, y) coordinates are captured by pressing SHIFT key\n"
               "and left mouse button click on canvas or you can enter the coordinates manually.")