fix symfony 2.8 deprecation warnings

[jwong-dayspring]

Fix deprecation warnings in Symfony 2.8 when using ModelType

The value "false" for the "choices_as_values" option of the "choice" form type (Symfony\Component\Form\Extension\Core\Type\ChoiceType) is deprecated since version 2.8 and will not be supported anymore in 3.0. Set this option to "true" and flip the contents of the "choices" option instead

The "choice_list" option of the "choice" form type (Symfony\Component\Form\Extension\Core\Type\ChoiceType) is deprecated since version 2.7 and will be removed in 3.0. Use "choice_loader" instead

Propel\Bundle\PropelBundle\Form\Type\ModelType: The FormTypeInterface::getName() method is deprecated since version 2.8 and will be removed in 3.0. Remove it from your classes. Use getBlockPrefix() if you want to customize the template block prefix. This method will be added to the FormTypeInterface with Symfony 3.0

Accessing type "choice" by its string name is deprecated since version 2.8 and will be removed in 3.0. Use the fully-qualified type class name "Symfony\Component\Form\Extension\Core\Type\ChoiceType" instead

Fixes #394

[marcj]

1.5 is actually unmaintained. I'd not touch this @havvg

[jwong-dayspring]

@marcj Do you mean Propel 1.5? There is no stable release of PropelBundle beyond 1.5.x right now.

[nibsirahsieu]

What about merging in branch 1.6? AFAIK, 1.6, is targeted for symfony 3

[jwong-dayspring]

It looks like the core part of this fix already made it into the 1.5 branch.