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Merge remote-tracking branch 'upstream/beta' into beta
Use Hikari Connection Pool instead of Postgres default, currently properties hacked around.
Replace ObjectStoreWriter connection if it has been closed somehow.
add config file to tutorial
Read properties for HikariCP connection pool, alter access to underlying PGConnection.
Update database connection properties for new connection pool.
Fix casting to PGConnection.
Export postgres jar.
Close the connection pool correctly.
Less log output of ids.
fix regular expression. Refs #692
notes for 1.3.8
Merge pull request #698 from intermine/uniprot-feature-hot-fix

Uniprot feature hot fix
Extend timeout when checking connection is still valid to avoid build errors.
Fewer connections to unittest db.
Generate better queries for empty collections.
Re-enable Null/Not Null constraints on refs/cols in query builder.
Prevent classes being added to the FROM list without being joined to anything.
Initial tests for null/not null references and collections.