Fix retryAfter delay, add dynamic delete delay, update default delays
-Fix Discord API reporting too short retryAfter (assumed need to convert to seconds, x3 for margin)
-Fix/add dynamic delete delay mechanism: +150ms every time rate limited, -50ms every 1000 deleted messages (about 22min at 1300ms)
-Update default delays to better reflect Discord rate limit
Update deletecord.user.js
Merge pull request #5 from larryqiann/delay-fix
Fix retryAfter delay, add dynamic delete delay, update default delays
