Various Improvements / Small Features

• $container parameter on a generator/value now injects a dynamically created child container into the object/function being built.
• Support for container chaining. Pass an existing container to .createContainer(parent) or simply call .createChild() on an existing container.
  • Parent containers can now contain incomplete dependency graphs, with child containers filling in the blanks.
• Can store and retrieve non-function/class/arrow values now, allowing injection of configuration string data.
• Code quality improvements (100% statement coverage, 95% branch coverage).