Added a method that fills in duplicate events in order to match a given segment sequence. This will be used to duplicate scan events to match label events. Improved comments, also noting that categorical sensor values are not allowed to be None (this has a special meaning in the add() method).
Added a method that fills in duplicate events in order to match a given segment sequence. This will be used to duplicate scan events to match label events. Improved comments, also noting that categorical sensor values are not allowed to be None (this has a special meaning in the add() method).

git-svn-id: 88c9ca70625627825018ef89be83f0d41a8e4cf1@13749 b56c7a7d-ac47-0410-a905-b6f7de78896a

ska-sa/katdal