Refactor and modernize namespace declarations

 * Completely remove inline namespace v2
 * Flatten some unnecessarily deep namespace nesting
 * Move DummyClientFace, Segmenter, SegmentFetcher to namespace ndn
 * Move all unit tests to namespace ndn::tests

Change-Id: I8bcfcf9fd669936a3277d2d5d505f765b4b05742
diff --git a/tests/unit/encoding/block.t.cpp b/tests/unit/encoding/block.t.cpp
index 8dd21d3..c93a307 100644
--- a/tests/unit/encoding/block.t.cpp
+++ b/tests/unit/encoding/block.t.cpp
@@ -31,8 +31,7 @@
 #include <cstring>
 #include <sstream>
 
-namespace ndn {
-namespace tests {
+namespace ndn::tests {
 
 BOOST_CONCEPT_ASSERT((boost::EqualityComparable<Block>));
 
@@ -751,5 +750,4 @@
 BOOST_AUTO_TEST_SUITE_END() // TestBlock
 BOOST_AUTO_TEST_SUITE_END() // Encoding
 
-} // namespace tests
-} // namespace ndn
+} // namespace ndn::tests