migrate to dhtnet namespace

Change-Id: I7143a010bd83e8cfa7a3c8c3072ed23f6f0ba8e3
diff --git a/src/string_utils.cpp b/src/string_utils.cpp
index 934ff23..3ab4359 100644
--- a/src/string_utils.cpp
+++ b/src/string_utils.cpp
@@ -40,7 +40,7 @@
 
 #include <ciso646> // fix windows compiler bug
 
-namespace jami {
+namespace dhtnet {
 
 #ifdef _WIN32
 std::wstring