Massive update containing several months of changes from the now-defunct private chip repo.

* Adds support for a L2 cache with directory bits for tracking L1 coherence (DefaultL2Config), and new metadata-based coherence API.
* Additional tests.
* New virtual memory implementation, priviliged architecture (1.7), custom CSRs, FDivSqrt unit
* Updated TileLink protocol, NASTI protocol SHIMs.
* Lays groundwork for multiple top-level memory channels, superscalar fetch.
* Bump all submodules.

project/plugins.sbt

@@ -0,0 +1,5 @@
+resolvers += "jgit-repo" at "http://download.eclipse.org/jgit/maven"
+
+addSbtPlugin("com.typesafe.sbt" % "sbt-ghpages" % "0.5.3")
+
+addSbtPlugin("com.typesafe.sbt" % "sbt-site" % "0.8.1")