Add flag for when application.createRenditions() is running

Only one createRenditions() call can be executing at any given time, so wait for the Promise it returns before calling it again.

Add flag to show if renditions are running.

if (application.renditionsAreRunning) { return }

Since renditions are asynchronous add flag to indicate if create renditions is available to call.

Use Case
Balinda has written a plugin that exports vectors of medical devices. Often she has 1000 renditions per project. She broken up exporting into groups and uses the renditions are running flag to check if export has finished.

if you await or .then the function inside only executes after the promise is returned.