sdbusplus: use shorter type aliases

The sdbusplus headers provide shortened aliases for many types.
Switch to using them to provide better code clarity and shorter
lines.  Possible replacements are for:
  * bus_t
  * exception_t
  * manager_t
  * match_t
  * message_t
  * object_t
  * slot_t

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I19e094a2a99893627dbb82b615f630b87ad90fdd
diff --git a/mainapp.cpp b/mainapp.cpp
index e8a1f00..9ae2ac4 100644
--- a/mainapp.cpp
+++ b/mainapp.cpp
@@ -25,7 +25,7 @@
 int main(int /*argc*/, char** /*argv*/)
 {
     auto bus = sdbusplus::bus::new_default();
-    sdbusplus::server::manager::manager objManager(bus, USER_MANAGER_ROOT);
+    sdbusplus::server::manager_t objManager(bus, USER_MANAGER_ROOT);
 
     phosphor::user::UserMgr userMgr(bus, USER_MANAGER_ROOT);