Add prototype
Add column type
Fix column pkg
Add generated tests to column pkg. Remove support for interface types since it is excessive for now.
Refactor to add automatic constructor
Add At() method to Column types
Add String() method an use byte instead of uint8 since, Printf(%#v) need this
Add missing String() method in interface
Add strng package for extracting typed data from strings
Refactored column package using strng extractors
Add missing tests. 100% coverage in column package
WIP AddRow