Remove {Static,}Object for Shallow Class Hierachy

[mariuswilms]

Base classes are set to be removed in 2.0, they have been deprecated in 1.2.

• [ ] Remove _init() usage, where tests rely on skipping the initialization phase, change classes to accept an alternative less-generically named option to skip certain parts of the initialization phase. The _init() class methods will than need to be merged into the constructor.
• [ ] Classes which rely on auto configuration currently present in the base class' _init() should make use of AutoConfigurable instead.
• [ ] Have the classes that were one level above the old base classes, set $_config
• [ ] Stop classes from extending deprecated base classes
• [ ] Ensure all unit tests are green
• [ ] Ensure all integration tests are green

The _init removal is being worked upon in the init-removal branch.

[nateabele]

I ended up maintaining the _init() functionality, as the complexity trade-off is low compared to the ability to bootstrap a class without its dependencies, and feedback from the community was that the migration burden would have been too significant.

This functionality has been incorporated into the AutoConfigurable trait.