Configuration of temp lock files

[getnito]

Today I was syncing a local folder to a local Google drive folder, and I realized that for various reasons it might be a good idea to provide a way to configure the location of the temporary lock (sync.ffs_lock) files for each tree. There might be situations where you don't want any writing to the source, or any writing at all to any tree during a compare only operation. There might also be situations where the source or destination is a special files system, (like Google drive) and constant writing to a file might cause unnecessary activity on such file system, disrupt it, or cause unintended consequences.
Having the option to specify a location for these lock files might be of use for unforeseeable situations. For example you might want to designate a location for all temp files, or a specific location/filename for each tree.

[addilapi]

+1 ... due to the way our network backups work these files are currently visible to our end users which is not ideal. It would be better if these were located somewhere outside of the folder pairs being configured for sync. My vote would be to allow for the use of a local ProgramData folder...