Add ability to emit 1 file per module (#443)

Changes Emitters to also be Transforms and use Annotations for both
telling an emitter to do emission as well as getting the emitted result.
Helper functions ease the use of the new interface. Also adds a
FirrtlExecutionOptions field as well as a command-line option. Use of 
Writers in Compilers and Emitters is now deprecated.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/main/scala/firrtl/annotations/Named.scala b/src/main/scala/firrtl/annotations/Named.scala
index 4b39c977..0e365249 100644
--- a/src/main/scala/firrtl/annotations/Named.scala
+++ b/src/main/scala/firrtl/annotations/Named.scala
@@ -14,6 +14,12 @@ sealed trait Named {
   def serialize: String
 }
 
+/** Name referring to the top of the circuit */
+final case object CircuitTopName extends Named {
+  def name: String = "CircuitTop"
+  def serialize: String = name
+}
+
 final case class CircuitName(name: String) extends Named {
   if(!validModuleName(name)) throw AnnotationException(s"Illegal circuit name: $name")
   def serialize: String = name