- Modified the Distance Tool such that the Measure button can't be clicked while measuring is in progress

- optimized selection of drills in the Excellon Editor
- fixed bugs in multiple selection in Excellon Editor
- fixed selection problems in Gerber Editor
- in Distance Tool, when run in the Excellon or Gerber Editor, added a new option to snap to center of the geometry (drill for Excellon, pad for Gerber)

FlatCAMApp.py

@@ -890,6 +890,9 @@ class App(QtCore.QObject):
             # Subtract Tool
             "tools_sub_close_paths": True,
 
+            # Distance Tool
+            "tools_dist_snap_center": False,
+
             # ###################################################################################
             # ################################ TOOLS 2 ##########################################
             # ###################################################################################