Ability to add/delete data table rows and columns Completed

At present, users can delete rows from the UI, but they are unable to add a new row, add a new column, or delete a column without creating a TSV in an external application. Having the ability to add or delete rows and columns in a data table from the Terra UI would save users time, especially if only minor additions or deletions are required. 

Deleting a column is a particularly arduous process because you have to:

1. Download all rows of the table
2. Delete the table in the Terra UI
3. Modify the downloaded TSV to delete the column(s) of interest
4. Re-upload the TSV