Make the dataReadOnly property of data-sources a column property

[nilshansen94]

The architecture of data-sources makes it possible to specify if a whole source is writable or not, using the dataReadOnly property. A very useful feature would be to make the dataReadOnly property a column property. With this, it would be possible to make certain columns writable, while others are read-only. For example, the name column of the Query-a-file-system source could be writable while the size column would be a read-only column.