Editability of cell
Editability of cell is dependent upon both global
In previous versions grid checks both global
If any of the options has false value or returns false value, then cell is read only, otherwise it's editable.
In recent version,
column.editable option has higher priority than global
Grid first checks value of former option and assigns editability to a cell accordingly.
Grid checks value of latter option only if value of former option is undefined / null.