Add job type parameter to Dispatch.cancelAll()

[fatcerberus]

Dispatch.cancelAll() currently takes no arguments and clears only now and later jobs. Sphere.shutDown() must be called to also clear any update and render jobs, which might be a bit confusing for someone reading the code when quitting the engine isn't the actual intent. Consider adding a job type parameter to cancelAll() to specify which type(s) of jobs need to be canceled.