Version 2.0.6 released

Changes from previous version:

• Object properties dialog: new tag editor with shortcut menu item "Edit tags" in the object menu.
• Object menu: new sub-menus "Add tag" (adds tag to the selected objects) and "Delete tag" (deletes tag from the selected objects).
• Replace tag dialog, replace field name dialog and replace field value dialog: added a drop-down list to the replace-with-value field.
• Added a prompt to delete the selected item from the recent file list if the file is not found.
• Minor user interface improvements.
• Updated example files.