server: minor refactoring

Move files into a server subdirectory to correspond to the 'server'
namespace and create a 'server.hpp' as method to gain includes
needed by any server instance.  Create a few type aliases to
reduce namespace levels.

Change-Id: I8f8ea8e57177393faa007351a540d08873d36632
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/tools/templates/method.mako.prototype.hpp b/tools/templates/method.mako.prototype.hpp
index 5e8f2ac..d8155c7 100644
--- a/tools/templates/method.mako.prototype.hpp
+++ b/tools/templates/method.mako.prototype.hpp
@@ -91,7 +91,7 @@
         sd_bus_message* msg, void* context, sd_bus_error* error)
 {
     ### Need to add a ref to msg since we attached it to an sdbusplus::message.
-    auto m = sdbusplus::message::message(sd_bus_message_ref(msg));
+    auto m = message::message(sd_bus_message_ref(msg));
 
     % if len(method.parameters) != 0:
     ${parameters_as_local()}{};