Add an option to disable cloud watch lite

This also adds a deprecation warning.
This also changes the default to use Ceilometer.

Release message:
Anyone deploying Heat should not be using OS::Heat::CWLiteAlarm, but
OS::Ceilometer::Alarm.
CWLiteAlarm should be explictly disabled in /etc/heat/heat.conf by
setting "enable_cloud_watch_lite=false". This will stop Heat from
running a period task check for alarms.

DocImpact
Change-Id: I2a10c14772bdafc001e211d7e94502ac1f6b32b1
Closes-bug: #1322128

etc/heat/environment.d/default.yaml

@@ -3,7 +3,7 @@ resource_registry:
     # allow older templates with Quantum in them.
     "OS::Quantum*": "OS::Neutron*"
     # Choose your implementation of AWS::CloudWatch::Alarm
-    #"AWS::CloudWatch::Alarm": "file:///etc/heat/templates/AWS_CloudWatch_Alarm.yaml"
-    "AWS::CloudWatch::Alarm": "OS::Heat::CWLiteAlarm"
+    "AWS::CloudWatch::Alarm": "file:///etc/heat/templates/AWS_CloudWatch_Alarm.yaml"
+    #"AWS::CloudWatch::Alarm": "OS::Heat::CWLiteAlarm"
     "OS::Metering::Alarm": "OS::Ceilometer::Alarm"
     "AWS::RDS::DBInstance": "file:///etc/heat/templates/AWS_RDS_DBInstance.yaml"

etc/heat/heat.conf.sample

@@ -70,6 +70,10 @@
 # stack locking. (integer value)
 #engine_life_check_timeout=2
 
+# Enable the legacy OS::Heat::CWLiteAlarm resource. (boolean
+# value)
+#enable_cloud_watch_lite=true
+
 # Deprecated. (string value)
 #onready=<None>