Identity in *-to-one association builder

[guiwoda]

Added the ability to set identity with associations through the ClassMetadataBuilder / AssociationBuilder classes.

Added multiple tests to ensure that all association scenarios behave as expected.

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[Ocramius]

@guiwoda the alignment in the code is messed up. Also, please only test bits relevant to your changes.

[Ocramius]

This assertion is too fragile

[guiwoda]

@Ocramius you mean in the tests?
I copy-pasted almost everything from previous tests. Could you point exactly what alignments are messed up? Or how would you do a less fragile assertion?

Also, all the tests I commited are related to my change. Please review it again if that's not clear.

[Ocramius]

I copy-pasted almost everything from previous tests

Please build smaller assertions then, checking things such as $this->assertSame(['foo' => 'bar'], $metadata->getIdentifier());

[Ocramius]

Poking @beberlei for a decision on whether we want this or not

[Ocramius]

Decided to merge, but will do as soon as I have free time to check it carefully.

[Ocramius]

Will merge as-is. If the tests are too fragile, we can reduce their scope later on.

[Ocramius]

Merged after a rebase at a13143b

[beberlei]

Please see b3a6fb7 for some changes to this behavior.

[guiwoda]

Great! I always found the "is" syntax confusing as a setter.