refactor(igor): Rename master to controller

[sikevux]

This change renames master to controller. The reasoning behind this change is that none of the services seems to be using that terminology anymore.

Changing the terminology in Igor to something that at least some of the services uses makes it easier to understand what's being referenced.

All externally accessible APIs with the old terminology are marked as deprecated and will use the new functions until the deprecated functions are finally removed. This to remain backward compatible.