Make DoctrineServiceProvider db connection lazy
merged branch igorw/doctrine-lazy-conn (PR #722)

This PR was squashed before being merged into the 1.0 branch (closes #722).

Discussion
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Make DoctrineServiceProvider db connection lazy

Specifically, do not create all connections early, only create them as
needed.

Commits
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9cf31e4 Make DoctrineServiceProvider db connection lazy