Options | Clarify when "Merge Option Settings" are used

[jfmdev]

On the Options screens, add a brief text bellow the "Merge Options Settings" explaining that these options are used when updating the settings from the File URL (either when done automatically or when clicking the "Update now" file).

Also, on the confirmation alert displayed when clicking the Import button, update the message (currently "Are you sure you want to override your local settings with these values?") to clarify that all current values will be overridden.