UG-107 Docu for: Undo Email related actions

- added capability for the upcoming undo feature
- ox.appsuite.user.sect.email.manage.movecopy: Add a note
- ox.appsuite.user.sect.email.remove.delete: Add a note, first draft

help/inline_help_capabilities.css

@@ -31,6 +31,7 @@ html.embedded.cap-spreadsheet .cap-spreadsheet,
 html.embedded.cap-switchboard .cap-switchboard,
 html.embedded.cap-tasks .cap-tasks,
 html.embedded.cap-text .cap-text,
+html.embedded.cap-undo .cap-undo,
 html.embedded.cap-webdav .cap-webdav,
 html.embedded.cap-webmail .cap-webmail,
 html.embedded.cap-xing .cap-xing,