Ticket #473: Add option of saving User ID in xml

Changes Made:
1. Choose if User ID is to be saved during import of divelogs from
subsurface webservice. Save function must be called once for change
to take effect.
2. Dialogbox retains the last set option.

Todo:
1. Discard the save option on loading new dive or changing dive.
2. Force save once on clicking accept ?

Signed-off-by: Venkatesh Shukla <venkatesh.shukla.eee11@iitbhu.ac.in>