Refactor package hierarchy and remove legacy bus protocol implementations (#845)

* Refactors package hierarchy.

Additionally:
  - Removes legacy ground tests and configs
  - Removes legacy bus protocol implementations
  - Removes NTiles
  - Adds devices package
  - Adds more functions to util package

src/main/scala/diplomacy/Nodes.scala

@@ -1,12 +1,12 @@
 // See LICENSE.SiFive for license details.
 
-package diplomacy
+package freechips.rocketchip.diplomacy
 
 import Chisel._
-import config._
-import util.HeterogeneousBag
-import scala.collection.mutable.ListBuffer
 import chisel3.internal.sourceinfo.SourceInfo
+import freechips.rocketchip.config.Parameters
+import freechips.rocketchip.util.HeterogeneousBag
+import scala.collection.mutable.ListBuffer
 
 // DI = Downwards flowing Parameters received on the inner side of the node
 // UI = Upwards   flowing Parameters generated by the inner side of the node