Add to Programming Metadata section

[laijasmine]

I was helping someone who has taken the course before and now they want to publish their own data. Filing this issue hoping to address some of the gaps when taking the example they used in the training to their own datasets.

(1) There was some confusion on what to do when you have multiple csv files and how to document them in the metadata
(2) How to add custom units

A small supplemental section so users that have taken the course can refer to it and if we are responding to emails we can easily point to as a resource.

(3) The relationship between the metadata and data ids in this section of code and how all these object relate to one another

# Add our data file to the package
sourceObj <- new("DataObject",
                 id = data_id,
                 format = "text/csv",
                 filename = "files/my-data.csv")

dp <- addMember(dp, sourceObj, mo = metadataObj)
dp

Something graphical to help connect the concepts might help so that it feel a little less abstract.