`.database.sqlitehouse` — Add SQLite annotation to designate foreign key relationships.

[zerobandwidth]

Following completion of issue #26, add a new annotation type allowing designation of a table column as a foreign key in another table.

Alter the discovery algorithms that manage creation and update of the database, such that they will discover these annotations and ensure that the tables are constructed in the proper order, to ensure that foreign key constraints are not created before the corresponding targets are defined.