Improve StatementsDao efficiency for reading

[carlgieringer]

Right now StatementsDao.readStatementForId reads the Statements one-by-one using readStatementWithoutSentenceForId (which uses readStatementsWithoutSentencesForIds for a single statement.) We should be able to use some combination of (or a new method that combines the approaches within) readStatementsWithoutSentencesForIds and readStatementChainForId to query the DB just once to get every thing we need for readStatementForId.

But since this may be early optimizing, consider the cost of improving (maybe start monitoring query performance first? #614)