Add check if custom action name is not already a default action

[matrxs]

This happened in the AIMS project, in which the OpenDoorAction of MATRXS and a custom identically named OpenDoorAction co-existed. This lead to highly unpredictable behaviour (but no warning or error), where the agent at seemingly random times used the custom and MATRXS action version alternately.

The MATRXS OpenDoorAction was imported in the default AgentBrain, which were extended in the custom AIMS Agent, the file which also contained an import for the custom OpenDoorAction