14: Research database migration tools

Researched and found Liquibase, which I believe is pretty widely used.

Implemented src/main/resources/create-db.sql as a Liquibase-formatted
SQL script and modified pom.xml to run before tests.

A temporary table named statusus_old was added as a temporary measure to
allow the unit and integration tests to continue to function.
PostgresStorage was modified to use the new table. Since we're creating
the tables via Liquibase, the createTable method was removed. Adding
this table is temporary, but allows us to exercise the Liquibase logic
in adding a changeset to remove the table when the code is properly
updated.

Also added a new dependency on org.mortbay.jetty:jsp-2.1 to avoid a
recently-cropped-up ClassNotFoundException when the Jetty container was
stopping. See
http://stackoverflow.com/questions/19553525/mavenseleniumjetty-classnotfoundexception-when-jetty-is-shutting-down#comment29560479_19699169
for more information.