button-handler: Add ID button actions

Creates a signal handler for the 'Released' signal.

The handler will toggle the 'Asserted' property in the
LED group defined by the configure file.  The default
group is 'enclosure_identify'.  The effect of this is
the LEDs in the group will toggle on or off on each
button press.

Tested: Used the 'simPress' method on the ID button object.

Change-Id: I9f68a8b3fae02efc7f6cfb6dbcf8a45cce7f2d9c
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c4e8483..0fa7a58 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -14,6 +14,7 @@
 set(LONG_PRESS_TIME_MS 3000)
 set(CHASSIS_STATE_OBJECT_NAME "xyz/openbmc_project/state/chassis")
 set(HOST_STATE_OBJECT_NAME "xyz/openbmc_project/state/host")
+set(ID_LED_GROUP "enclosure_identify" CACHE STRING "The identify LED group name")
 
 add_definitions(-DPOWER_DBUS_OBJECT_NAME="/${POWER_DBUS_OBJECT_NAME}0")
 add_definitions(-DRESET_DBUS_OBJECT_NAME="/${RESET_DBUS_OBJECT_NAME}0")