Add ControllerInterfaceBase class with methods for chainable controller

[destogl]

Following the disucssion in #663 (#663 (review)), and on destogl#11 this PR introduces a new base class for controllers interfaces from which "normal" controller implementing ControllerInterface and "chainable controllers" implementing ChainableControllerInterface are derived.

In the second commit loading of controllers inside controller manager is updated resulting that users export their controllers as usual, using ControllerInterface and not ControllerInterfaceBase class.
This provides nice user API. (This will then also enable users to export plugins for chained controllers using ChainableControllerInterface class).

[bmagyar]

Two small notes, otherwise looks pretty clean to me!