Use std::move in more places

Plus various code simplifications

Change-Id: I19805e4a635e4c74afaff68f9d8968475217ec6e
diff --git a/src/name-component.hpp b/src/name-component.hpp
index 47b6b93..cf39e58 100644
--- a/src/name-component.hpp
+++ b/src/name-component.hpp
@@ -458,7 +458,7 @@
    * @brief Create ImplicitSha256DigestComponent component
    */
   static Component
-  fromImplicitSha256Digest(const ConstBufferPtr& digest);
+  fromImplicitSha256Digest(ConstBufferPtr digest);
 
   /**
    * @brief Create ImplicitSha256DigestComponent component