Inherifromrm Async Actor, Track if the Iterator is running, first draft of library documentation

- �The Iterator Actor now inherits from Async Actors, this allows removing the Actor Core method and all the event refnums used to communicate with it and replacing it with an Async method that will send the iteration commands. The "Start Iteration" method then just starts such Async method (Closes #1)
- Added an internal flag, called "Iterating" indicating that the iterator is running. If the flag is true and we start an iteration we should do nothing. If we try to stop an Iterator that is not running we should do nothing. See #2
- Added the first draft of library documentation see #5

Author: AndreaV-Lsi