(data): Migration v4 -> v5.

Add migration script for v4 -> v5.
Bump data version in schema and constants.

data/schema.sql

@@ -4,7 +4,7 @@ CREATE TABLE VersionHistory(
   time TIMESTAMP WITH TIME ZONE DEFAULT CURRENT_TIMESTAMP NOT NULL,
   author TEXT
 );
-INSERT INTO VersionHistory (version, author) VALUES (4, 'Initial Creation');
+INSERT INTO VersionHistory (version, author) VALUES (5, 'Initial Creation');
 
 
 CREATE OR REPLACE FUNCTION update_timestamp_column()