CSVObject:
- Added inner class EmptyCell to denote a cell with no data in it (since
an empty string could be data and 'null' causes problems
- Added methods for getting and setting column names
- Added methods for retrieving rows and columns
- Amended constructor to throw new type of exception where more
appropriate
CSVDataException:
- Created new exception for errors relating to the data in a CSVObject
that are unrelated to file IO