implement session stat command

Implement the session stat command.

Change-Id: I1ff715dd32d963722182db84b475bc9adbfcc7ea
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/src/ipmiblob/blob_handler.hpp b/src/ipmiblob/blob_handler.hpp
index 22ad5f5..a663b63 100644
--- a/src/ipmiblob/blob_handler.hpp
+++ b/src/ipmiblob/blob_handler.hpp
@@ -63,6 +63,11 @@
     /**
      * @throws BlobException.
      */
+    StatResponse getStat(std::uint16_t session) override;
+
+    /**
+     * @throws BlobException.
+     */
     std::uint16_t openBlob(const std::string& id,
                            std::uint16_t handlerFlags) override;