Update DI system with DSL for configuring bindings

[jvz]

I first came up with this idea while working out how to remove the need for loading classes from an unknown ClassLoader that I needed a couple updates to the DI system:

• Add a @TestBinding repeatable annotation for making it easy to register custom test bindings for a test. As it stands now, the only way test bindings could be specified was via methods on the test class to register said class as a bundle. This approach does not work with tests that use constructor injection for JUnit extension-provided arguments, thus requiring a different mechanism for test bindings. This should clean up the various test extension code in log4j-core-test.
• Add a DSL to DI to make it simpler to register bindings that are registered either before or after the list of ConfigurableInstanceFactoryPostProcessor services are invoked.

Since the original branch for that code spiraled into a tangent branch, I'm breaking up the changes there into relevant pieces.

[jvz]

Completed