VPP Python language binding - plugin support

- Moved Python generator tool to tools directory
- Added build-vpp-api Makefile target
- Generator now only creates a Python representation of the .api
  the rest of the framework is in the vpp_papi script
- Each plugin has its own namespace.
- Plugin Python files are installed in vpp_papi_plugins for easy
  use inside the build tree.

Change-Id: I272c83bb7e5d5e416bdbd8a790a3cc35c5a04e38
Signed-off-by: Ole Troan <ot@cisco.com>
diff --git a/vppapigen/node.c b/vppapigen/node.c
index e66fdce..420a128 100644
--- a/vppapigen/node.c
+++ b/vppapigen/node.c
@@ -1339,6 +1339,11 @@
     np = np->peer;
   }
   fprintf (fp, "\n]\n");
+
+  /*
+   * API CRC signature
+   */
+  fprintf (fp, "vl_api_version = 0x%08x\n\n", (unsigned int)input_crc);
 }
 
 void generate(YYSTYPE a1)