see symfony/symfony#14050 for more details and https://github.com/symfony/symfony/blob/2.7/src/Symfony/Component/Form/CHANGELOG.md and https://github.com/symfony/symfony/blob/2.7/UPGRADE-2.7.md#form

• A) choice_list was deprecated, replaced with choices_as_values or choice_loader
• B) From UPGRADE-2.7.md: You should flip the keys and values of the "choices" option in ChoiceType and set the "choices_as_values" option to true. The default value of that option will be switched to true in Symfony 3.0. (I'm not sure what this actually means). There is also some new choice_value option - not sure how it relates.
• C) ChoiceListInterface namespace changed
• D) ChoiceView namespace changed AND order of arguments changed
• E) ChoiceList was deprecated in favor of DefaultChoiceListFactory
• F) property option of DoctrineType is now choice_label
• G) EntityChoiceList was deprecated, now use DoctrineChoiceLoader