Nest all namespaces

The compiler supports this now.  We can type less going forward.
No functional changes.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I29d6fa4f9aacc0e381f1a7637294db0392466995
diff --git a/y2019/actors/autonomous_actor.cc b/y2019/actors/autonomous_actor.cc
index b8024ec..5200fed 100644
--- a/y2019/actors/autonomous_actor.cc
+++ b/y2019/actors/autonomous_actor.cc
@@ -10,8 +10,7 @@
 #include "y2019/actors/auto_splines.h"
 #include "y2019/control_loops/drivetrain/drivetrain_base.h"
 
-namespace y2019 {
-namespace actors {
+namespace y2019::actors {
 
 using ::aos::monotonic_clock;
 using ::frc971::ProfileParametersT;
@@ -392,5 +391,4 @@
   return true;
 }
 
-}  // namespace actors
-}  // namespace y2019
+}  // namespace y2019::actors