Update the `LaunchAtLoginController` code Fixes #1893

Returning CF types from an Obj-C method always seems a bit funny, so I changed the problematic method to a C function, and renamed it to follow the Obj-C naming conventions.

You should probably take a look at [my commit](https://github.com/quicksilver/LaunchAtLoginController/commit/d117c10f152a2f02092fddf7c444e64002d2fef6) on the `LaunchAtLoginController` repo whilst you're at it.
I merged the two of the 3 outstanding pull requests on the original LALC repo before making my changes (although they weren't very well written anyway)