include motusTagDepID in section 5.3 on data cleaning duplicate tags

[plorch]

Since many or most projects have duplicate tags, and since the example data does not, the sample data limits the usefulness of the MotusRBook. Would it be possible to either add duplicate tags to the sample data, or change the text to suggest how to modify the example code to deal with duplicate tag deployments? It could be as simple as adding something like "If you followed the suggestion in section 4.3.4 and added a variable combining motusTagID and tagDeployID (e.g., motusTagDepID), substitute that variable for motusTagID in the example code below." after the paragraph "In the sample data, all tags were deployed only once, and so we use the motusTagID as a unique identifier for a tag deployment in all R code throughout the book."