Performance: Automatically adjust next poll period to account for network latency

[RolandPheasant]

High cpu usgae has been reported see issue #14

I think this is caused by the work to check for and load changes from the file is longer than the poll interval. So to remedy I will try the following

1. Slow down poll rate
2. Only start timer for next poll after the work in the previous poll is complete

[RolandPheasant]

Changed the way that files are polled.