Fix EnvironmentAware#environment_id when building entries or assets

[timfjord]

Currently both content_type.entries.new and environment.assets.new(basically ContentTypeEntryMethodsFactory#new and EnvironmentEntryMethodsFactory#new) don't work corrently when enviorment is not master. An object that is returned is always targeted to master

content_type.entries.new case

In this case, enviorment_id doesn't calculate properly, because sys doesn't really have any information about the current environment. But there is content_type reader that has #enviorment_id.

environment.assets.new case

In this case, sys[:enviorment] is present, but it is not Contentful::Management::Link, it is Contentful::Management::Environment.

This PR extends EnvironmentAware#environment_id and adds support for both cases. It might even fix other similar cases

It would be great to cover that with integrations specs. Unfortunately, I don't have access to the testing Contentful account, so I can just draft the specs but they need to be finalised by someone with the access

[timfjord]

For some reasons content_type&environment_id raises https://travis-ci.org/contentful/contentful-management.rb/jobs/537759420

[HQ063]

This must be merged, is an important fix, the current behaviour is clearly bugged.

[dlitvakb]

Hey @Timsly and @HQ063,

Sorry for the delay, merging and adding tests, will release as soon as possible.

Cheers

[dlitvakb]

Released in 2.10.0

[timfjord]

Thanks @dlitvakb 👍