Added FixtureAwareContextInterface to easily load fixtures from Context

[tPl0ch]

• Added Interface
• Added check for implmentation in context and subcontexts
• Added override of 'scenario' lifetime when context fixtures are present
• Added needed class vars to check if fixtures are already cached
• Added branch alis to composer.json

[robocoder]

I pushed your changes to this branch: https://github.com/vipsoft/DoctrineDataFixturesExtension/tree/tPl0ch-feature-fixture-aware-interface

I'm going to do some refactoring and add some much-needed unit tests, but I want to re-evaluate the changes to the HookListener.

[tPl0ch]

I am closing this now to clean my list of open PRs that I forgot :)