Better merging of collection types

[brutal-factories]

This reopens the previous PR #40 , which got closed by an erroneous force-push on my part

[dbu]

very cool, thanks a lot!

can you add a changelog entry that explains what the new functionality does? (and mentions that users don't need to change anything yet - apart from using PropertyTypeIterable instead of PropertyTypeArray when they extend functionality, to be forward compatible)

[dbu]

once i merged, i will merge 1.x to 2.x so that we can see only the changes for version 2.x in PR #43

[dbu]

awesome, thank you.

[dbu]

shall i tag a 1.x release for this?

[brutal-factories]

shall i tag a 1.x release for this?

Yes, could you also bump up liip/serializer and liip/serializer-jms-adapter?

[dbu]

i will wait so we can first add the forward compatibility methods and add deprecations.

and for liip/serializer we should add the handling of generic traversable.

[dbu]

https://github.com/liip/metadata-parser/releases/tag/1.2.0

we should now upgrade liip/serializer to require parser ^1.2 and avoid the deprecations.