Add AnnotationSpec file which provides an example of a way to implement...

Add AnnotationSpec file which provides an example of a way to implement generation of annotations in a chisel circuit that could be used by custom firrtl passes
This spec also shows and tests in a limited way the new API of .signalName, .pathName, parentModName which allows access to the various path information of a chisel component (something that subclasses SignalId, most prominently SubClasses of Data and Module