Add missing ids in exception message

[deguif]

Display ids of missing objects in exception message when ignore_missing option is used.

[deguif]

I added this information, as currently the exception display the list of all the ids, but to get the missing id(s), it requires to check manually which id(s) is/are missing.
This is easier to spot the missing id(s) and do something with them.

[XWB]

You will have to change the unit test as well:

1. FOS\ElasticaBundle\Tests\Unit\Doctrine\AbstractElasticaToModelTransformerTest::testAnExceptionIsThrownWhenTheNumberOfFoundObjectsIsLessThanTheNumberOfResults with data set #0 (array(Elastica\Result Object (...), Elastica\Result Object (...), Elastica\Result Object (...)), array(FOS\ElasticaBundle\Tests\Unit\Doctrine\Foo Object (...), FOS\ElasticaBundle\Tests\Unit\Doctrine\Foo Object (...), FOS\ElasticaBundle\Tests\Unit\Doctrine\Foo Object (...)))
   Failed asserting that exception message 'Cannot find corresponding Doctrine objects (0) for all Elastica results (3). Missing IDs: 1, 2, 3. IDs: 1, 2, 3' contains 'Cannot find corresponding Doctrine objects (0) for all Elastica results (3). IDs: 1, 2, 3'.

[deguif]

Maybe we should find a better wording for the exception message, but I'm not the best for this kind of things.

[XWB]

It's fine for now :)