Make poll_delay in egnyte/events.py configurable

[ssivatws]

poll_delay is set to 1.0 by default and we want it to configurable and want custom polling like once ini 30 seconds or 45 seconds.

Making frequent calls every 1 second to events API sometimes leads to rate limiting by Egnyte API.

Expecting something like config file in parent directory or env variable where custom poll delay can be set.