Allow configuration to control log file name as well as directory

[adobeDan]

(requested by @cgravatt) User Sync names its log files for the date it runs, which is handy because it automatically accomplishes a simple form of log rotation. However for users who wish to do their own log rotation (e.g., using logrotate), this ever-changing file name convention is an impediment, not a convenience. It would be great to have User Sync provide a format string for the log file name, with a default value equal to its current value. This would be a backwards-compatible change that would allow users who need a fixed name to override the default.

[adobeDan]

No further updates from the contributor, so this will wait for the next feature release.