util: rename digest.hpp to sha256.hpp

The new file name matches the Sha256 class included within.

This commit also deletes deprecated crypto.hpp.

refs #3940

Change-Id: Ib9bbcd0ba087b812bb0886ceaea116689d4633f5
diff --git a/src/name-component.cpp b/src/name-component.cpp
index 34a3470..045d5f2 100644
--- a/src/name-component.cpp
+++ b/src/name-component.cpp
@@ -27,7 +27,7 @@
 
 #include "encoding/block-helpers.hpp"
 #include "encoding/encoding-buffer.hpp"
-#include "util/digest.hpp"
+#include "util/sha256.hpp"
 #include "util/string-helper.hpp"
 
 #include <boost/algorithm/string/trim.hpp>