Column: Handle insertion of NULL valued columns
Column: Allow fetching a column value from its schema.

This will help load the value of a foreign key
Revert back to a single insertion at a time.

This will allow us to fetch the autoincrement value for PKeys
Force int type for primary keys
Enable primary key autoincrement
Tests: rely on autoincrement for primary key value
Fetch new primary key auto incremented value after insertion
Add missing makefile
Tests: enable more warnings
Tests: Fix warnings
Avoid having non-trivial statements in check macros