LibCore: Put all classes in the Core namespace and remove the leading C

I've been wanting to do this for a long time. It's time we start being
consistent about how this stuff works.

The new convention is:

- "LibFoo" is a userspace library that provides the "Foo" namespace.

That's it :^) This was pretty tedious to convert and I didn't even
start on LibGUI yet. But it's coming up next.

DevTools/Inspector/RemoteProcess.cpp

@@ -34,7 +34,7 @@
 RemoteProcess::RemoteProcess(pid_t pid)
     : m_pid(pid)
     , m_object_graph_model(RemoteObjectGraphModel::create(*this))
-    , m_socket(CLocalSocket::construct())
+    , m_socket(Core::LocalSocket::construct())
 {
 }
 
@@ -152,7 +152,7 @@ void RemoteProcess::update()
         }
     };
 
-    auto success = m_socket->connect(CSocketAddress::local(String::format("/tmp/rpc.%d", m_pid)));
+    auto success = m_socket->connect(Core::SocketAddress::local(String::format("/tmp/rpc.%d", m_pid)));
     if (!success) {
         fprintf(stderr, "Couldn't connect to PID %d\n", m_pid);
         exit(1);