Use std::move in more places

Plus various code simplifications

Change-Id: I19805e4a635e4c74afaff68f9d8968475217ec6e
diff --git a/src/data.hpp b/src/data.hpp
index d70f509..56f98ed 100644
--- a/src/data.hpp
+++ b/src/data.hpp
@@ -181,7 +181,7 @@
    *  @return a reference to this Data, to allow chaining
    */
   Data&
-  setContent(const ConstBufferPtr& value);
+  setContent(ConstBufferPtr value);
 
   /** @brief Get Signature
    */