Added ArrayCollection::createFrom.

[Bilge]

This allows derived classes to specify how new instances should be created when constructor semantics have changed. Without this, derived classes that modify constructor semantics have to re-implement the four affected methods using copy and paste because all hard-coded calls to new static($elements) are invalid.

🔖 I would appreciate a new tag for this PR.

[Ocramius]

From the IRC logs, here's the "why" behind this PR:

• consumer may sub-class ArrayCollection
• sub-class of ArrayCollection may define public function __construct(HahaSomething $else)
• these methods would crash due to new static() (should use new self() or allow delegations, like done in this PRs)

The issue is that ArrayCollection has been designed A LOT OF TIME AGO, and hasn't been made final. This leads to very fragile subclasses, because the design is not extensible by itself.

We can't make ArrayCollection final though, as it's extensively extended everywhere, and even extended within ORM and ODMs. Therefore we'd break BC after multiple major versions, and with large warning upfront.

The proper solution would be to implement Collection in subclasses, but meanwhile, this patch is an acceptable fix. Tests representing the scenario described above are still required here though.

[Bilge]

@Ocramius Test added. I also got rid of that shitty bootstrap.

[Ocramius]

👍 thanks!