Method for speech synthesis in the action SM base class

[alex-mitrevski]

Problem description

In order to make our actions more interactive/interpretable to outside observers, it might make sense to have a generic way of synthesising speech from within the actions. Right now, this has to be done by creating an appropriate publisher in every action where this functionality is desired.

Suggested solution

Add a say method to the action base class just like in ScenarioStateBase. This however means that the action base class should ideally be moved to the ros package in this repository since we do speech synthesis through ROS.