Service- und Actionclients missing in templates

[abubeck]

While code for action and serviceservices is generated, the templates are missing implementations of clients.
Both for c++ and python templates.

[floweisshardt]

it is important to have the clients generate from the model. If we let the user do that, we might get problems with remapping later on (if the names in the code don't fit the names in the model).

Simple solution: we could just add the client in the init/constructor function to make sure the name fits to the model:
cpp:
{{{actionlib::SimpleActionClient<learning_actionlib::FibonacciAction> ac("fibonacci", true);}}}
python
{{{self.client = actionlib.SimpleActionClient('fibonacci', actionlib_tutorials.msg.FibonacciAction)}}}