Add concept for Field, FieldData and Field Based Data Object
Replace ColumnSpec with ColumnConfig which includes ability to
define Extractor for the column.
Merge pull request #22 from sarality/fields

Fields
Merge pull request #23 from sarality/column_config

Replace ColumnSpec with ColumnConfig which includes ability to
Merge pull request #24 from sarality/sms_store

SmsMessafe is now based on Fields
Merge pull request #25 from sarality/master

Merging changes from Master