Make use of rhandsontable's read only features

[amoeba]

Stemming from https://github.com/ropensci/software-review/issues/426, @tdjames1 mentions we might benefit from using rhandsontable's read only functionality to prevent editing of certain columns.

This would be a good improvement to the Shiny apps and maybe even a good external contribution if someone was interested in taking this on.