Introduced comments and styled debug prints.
Structural refactoring:
search_columns, retrieve_columns, bind_datatypes
search_fk, search_fk_constr.
Work in progress.
Moved search functions dependent on
column data from VirtualTable class
to Column class. Work in progress.
Refactored retrieve functions dependent on
data columns. Moved from VirtualTable class
to Column class.
Tested and debugged refactoring.
User-space tests successful.