Allow transitive endpoint keywords.

[Mognom]

Allow components output endpoints to have the same keywords that are connected to one of its input endpoints.

This could be useful for any component that can operate with a generic input and wants to keep the keywords of the source on the output, making it easier to keep track of the keywords of the output and what should be connected with those components.

E.g: If an endpoint with keywords "test" is connected to input 1 of a component, allow output 1 to update its friendcode list adding "test" to it.