User Facing Firrtl Annotation API

Create new Annotation object which is a container for new annotation classes and functionality
Add annotate method to Module
Add Optional annotation parameter to Circuit case class, default is empty Seq
Add Annotaion ArrayBuffer to Dynamic Context, Builder.build will resolve component names during elaboration
Modified the earlier AnnotationExample to show use of new annotation system, remove annotations from GCD example
Enhance dumpFirrtl to dump any annotations present, uses the firrtl file name as a template