(bug 42688) terms search key schema update for sqlite

- adding a column with NOT NULL and existing data will fail
- note that sqlite also has the option of setting COLLATE NOCASE for the column and index,
but prefer to keep things consistent here with how we handle mysql.

Change-Id: I25bb707afaa73417ba6d2cc1f99f374cd682b590
Merge "(bug 42688) terms search key schema update for sqlite"