allowing multiple calls to cxy_ctl:init/1

[marcelog]

Hey :)

I have the following use case, where an application has multiple dependencies trying to set their own concurrency limits. I've figured that it wouldn't hurt to allow multiple calls to cxy_ctl:init/1, so each dependency could allow its own concurrency limits along the way (and/or adding limits when needed, instead of being a one-time only operation).

Makes sense?

[jaynel]

This issue will be resolved using three separate calls:

1. init => create cxy_ctl ets table and setup initial limits (or none if [] passed in)
2. add_task_types => only add new non-existing task type limits
3. remove_task_types => only remove existing task type limits

Removing a task type will cause crashes if you continue to try to run tasks of that type (or have existing tasks that have not completed yet).

New issues will be opened for the following items:

1. adjust_task_limits => sets new concurrency limits for a task type
2. remove_task_types should safely
   a) set limit to 0
   b) remove the type when the active count goes to 0 for both inline and spawned processes

[jaynel]

Fixed by #21