Add base support for GPIO presence

This is the starting code needed to build the application.

Change-Id: I46112a222afbc057ac4fc4f8fb2b4c83822023df
Signed-off-by: Gunnar Mills <gmills@us.ibm.com>
diff --git a/Makefile.am b/Makefile.am
index d664672..bbe24fc 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -17,4 +17,4 @@
                                  $(PHOSPHOR_LOGGING_CFLAGS) \
                                  $(LIBEVDEV_CFLAGS)
 
-SUBDIRS = test gpio-util
+SUBDIRS = test gpio-util presence