Rename FileBody to HttpBody

Now that our custom body type does things more than files, it makes
sense to rename it.  This commit renames the header itself, then all
instances of the class.

Tested: Basic GET requests succeed.
Change-Id: If4361ac8992fc7c268f48a336707f96e68d3576c
Signed-off-by: Ed Tanous <ed@tanous.net>
diff --git a/http/http_response.hpp b/http/http_response.hpp
index dca7682..afd51c1 100644
--- a/http/http_response.hpp
+++ b/http/http_response.hpp
@@ -1,5 +1,5 @@
 #pragma once
-#include "http_file_body.hpp"
+#include "http_body.hpp"
 #include "logging.hpp"
 #include "utils/hex_utils.hpp"
 
@@ -23,7 +23,7 @@
     template <typename Adaptor, typename Handler>
     friend class crow::Connection;
 
-    http::response<bmcweb::FileBody> response;
+    http::response<bmcweb::HttpBody> response;
 
     nlohmann::json jsonValue;
     using fields_type = http::header<false, http::fields>;