Update KeyValueRowType for Symfony 3.

[ubermichael]

At some point Symfony dropped SimpleChoiceList, and stopped referring to choice widgets by name. This patch updates those two things.

It may need back-porting to Symfony 2.8, I'm not sure.

[Burgov]

Can anyone verify that this is safe to merge without breaking older versions?

[pmdc]

It will be breaking projects with Symfony older than 2.7 as Symfony\Component\Form\ChoiceList\ArrayChoiceList was introduced in 2.7.

It will also break projects running on PHP 5.4 and lower as ::class constant was introduced in PHP 5.5.

Except for Symfony 2.3 (support ending in may 2017), the Symfony and PHP versions that would break are all unsuported.

[Burgov]

I guess we should wait until June before merging this?

[Burgov]

Is this good to go now? @pmdc

[enekochan]

May be this could be merged to a new v2.0.0 (where we would target Symfony 3.3, 3.4 and 4.0) and leave v1.4.x BC for 2.8 and/or 3.0. Either way there are more things that should be changed to be Symfony 3.4 compatible like:

https://github.com/Burgov/KeyValueFormBundle/blob/master/Form/Type/KeyValueType.php#L54
https://github.com/Burgov/KeyValueFormBundle/blob/master/Form/Type/KeyValueType.php#L83

[mvehar]

Will this be merged and published anytime soon?