SLC: Add logic in for connecting/handling splitters

[elenya-grant]

SLC: Add logic in for connecting/handling splitters

Currently, splitters are not connected to the SLC. These would likely be very important control points in the system and would perhaps require some special handling and connection to the SLC and the components that are connected to it. We should think about adding in connections to the SLC for splitters and logic in the SLC baseclass to handle splitters.

[elenya-grant]

Thoughts on this: to keep H2I flexible to the broad set of potential use-cases, user's should be able to specify which (if any) splitters can be controlled by the SLC vs which ones the SLC should not have access to change. Aka - if a user should be able to specify which splitters the SLC can change the inputs for vs which ones it can't.