GREG-7: Simple task running functionality. Adding ask for checking roles about to expire

This branch contains a simple setup for running tasks that we want to run at regular intervals, and a simple task for creating notification for roles that will expire in one month.

It is basically just a command that can start a process that will run a loop over tasks we have defined, while keeping track of when the task last completed. If needed it is easy to add some more functionality so make the scheduling a bit more intelligent (like specifying a time each task should run), but I don't think there is a need now.

The task that checks for roles about to expire is also basic. It could be made more robust by remembering which roles it has handled, but not sure it is needed to introduce that complexity.