Heat template dependency of service type

gistfile1.py

Suppose we want to provide custom heat template for specific service type.
Now trove uses only one heat template for VM pre-configuration and guestagent launching.

-----------------------------------------------------------------------------------------

We should provide dependency between service(mysql, percona, mongo, redis, cassandra) 
and specific heat template.

Also, we should externalize heat template from trove.common.template
to trove.extensions.service."service_type".template_module
-----------------------------------------------------------------------------------------

This is what Trove does now:
heat_template = template.HeatTemplate().template()
        parameters = {"KeyName": "heatkey",
                      "Flavor": flavor["name"],
                      "VolumeSize": volume_size,
                      "ServiceType": "mysql",
                      "InstanceId": self.id,
                      "AvailabilityZone": availability_zone}
        stack_name = 'trove-%s' % self.id
        stack = client.stacks.create(stack_name=stack_name,
                                     template=heat_template,
                                     parameters=parameters)
        stack = client.stacks.get(stack_name)
-----------------------------------------------------------------------------------------
What it should do:
This is what Trove does now:
service_template_class = 
	utils.import_class('trove.extension.service.%d.template' 
			   % service_type)
service_template = service_template_class()
if hasattr(service_template, 'get_template'):
	heat_template = service_template.get_template()
	        parameters = {"KeyName": "heatkey",
	                      "Flavor": flavor["name"],
	                      "VolumeSize": volume_size,
	                      "ServiceType": "mysql",
	                      "InstanceId": self.id,
	                      "AvailabilityZone": availability_zone}
	        stack_name = 'trove-%s' % self.id
	        stack = client.stacks.create(stack_name=stack_name,
	                                     template=service_template,
	                                     parameters=parameters)
	        stack = client.stacks.get(stack_name)