Allow the code and the DB to have different but compatible schemas.

We check for compatibility by specifying a schema version and minimum
schema version in the code, storing them in the DB, and checking whether
the DB is too old for the code or vice versa.

briar-api/src/org/briarproject/api/db/DbSchemaException.java

@@ -1,10 +0,0 @@
-package org.briarproject.api.db;
-
-/**
- * Thrown when the schema of the database differs from the schema expected by
- * the code.
- */
-public class DbSchemaException extends DbException {
-
-	private static final long serialVersionUID = -4444069279533651710L;
-}