Matched parameters' values are always strings

[mgv99]

When getting the value of a matched parameter in a state body, e.g.
temperature = predicted_intent.get_parameter('temperature').value
we always obtain a str object, therefore, we cannot do if temperature > 0, since it is a string object. We can simply cast the object to its proper type, but it adds complexity to the body of the state.
We could implement a flexible type value, at least for the following basic types:

• str
• int
• float
• datetime
• bool (can a user actually write a bool value in a message?)