Add a test for dependency inferrence
Mostly fixing problems related to getting inference working

Also:
* Simplify blueprint's builder method
* Adding a new tag role for injection-friendly blueprints
* Injectors now work with blueprints rather than artifacts (working with
  artifacts was a design error)
* Made some of the blueprints injector-friendly and added a built_injector
  blueprint to provide built blueprints that are injector-friendly
* Add dependencies => ... option to Bolts.pm artifact sugar
* Add builder {} sugar to Bolts.pm
* Add acquire() sugar to Bolts.pm