Allow BT::AnyTypeAllowed as port type and setOuput using BT::Any

[robin-mueller]

This pull request enables to use BT::AnyTypeAllowed when specifying the type of a port, basically meaning that this port has no static type and the node will determine the type of the variable dynamically.

See #893

[facontidavide]

thanks for the suggestion. I wonder how this should be documented in the tutorials.

What will it be the expected difference when usinf Any or AnyTypeAllowed?

[robin-mueller]

I also find it quite difficult to comprehensibly document the feature of allowing dynamically evaluated port types with the current implementation. My suggestion is more of a workaround to at least not break the scripting language when trying to do that. As I said, it would be more intuitive, if there was a single type that should be specified when declaring the port and when calling setOuput.

What was the initial intention behind allowing BT::Any in setOuput? Maybe we only allow BT::AnyTypeAllowed beside the common types when declaring a port. To me it feels wrong to allow BT::Any if it breaks the scripting language. Then we would have a more concise way of implementing that idiom.