Reduce number of Datastore read operations.

[MattHeard]

• Combine story beginning data into each story page to avoid loading the story beginning for every page.
• No object should ever be loaded more than once per page load.

[MattHeard]

First, log messages for every query, create, read, update, and delete.

[MattHeard]

Being logged in appears to cause an approximately 30 extra queries. Why?

[MattHeard]

I have made a spreadsheet with the current number of operations for each action:

https://docs.google.com/spreadsheets/d/18fm1pLCo502Sl2MWKbUQvqnYstClUhza5dprWeeemXQ/edit?usp=sharing

[MattHeard]

When logged in, the /preferences page performs about 142 queries and 70 read operations. WHY?!

[MattHeard]

On the latest test, when /preferences is accessed:

• Model.countMatchingEntities() calls PreparedQuery.countEntities(FetchOptions fetchOptions) 70 times,
• Notification.countNewNotificationsForRecipient(final String recipientId) calls PreparedQuery.countEntities(FetchOptions fetchOptions) 2 times, and
• Model.getSingleEntity(final PreparedQuery preparedQuery) calls PreparedQuery.asSingleEntity() 70 times.

[MattHeard]

Commit 5333546791e12f92188c4b131e73b6fd2ee35ea3 produced the following changes:

• 70% reduction in queries when logged in, and
• 75% reduction in read operations when logged in