Executed when the user clicks the edit repository image from the Repository Login Dialog
It presents an edit dialog where the user can edit information about the currently
selected repository
Describes a single field in an excel file
TODO: allow the width of a column to be set --> data.sheet.setColumnView(column, width);
TODO: allow the default font to be set
TODO: allow an aggregation formula on one of the columns --> SUM(A2:A151)