VCL: application proxy configuration

- Add support to configure VCL to set
  application proxy transport types
  and app_is_proxy flag via vcl
  config file or env vars.
- Clean up debug output.
- Rename session_scope -> app_scope.

Change-Id: I6e35f3cdd84daf0112133af8f33acd0152f87ca3
Signed-off-by: Dave Wallace <dwallacelf@gmail.com>

src/vcl/vcl_test.conf

@@ -22,10 +22,11 @@ vcl {
   app-timeout 54.3
   session-timeout 66.6
   accept-timeout 0.1
-  session-scope-local
-  session-scope-global
+  app-proxy-transport-tcp
+  app-proxy-transport-udp
+  app-scope-local
+  app-scope-global
   namespace-id 0123456789012345678901234567890123456789012345678901234567890123456789
   namespace-id Oh_Bother!_Said_Winnie-The-Pooh
-  namespace-secret 0x42bada55e5
   namespace-secret 42
 }