[lipstick] serialize/hide devicelock plugin arguments

Do not merge untill devicelock encryption plugin pull request have been merged.
This pull request serializes commandline arguments so it can be piped into encryption plugin's stdin.

EDIT: new devicelock plugin has now been merged to devel. So its when this receives LGTM then someone with merge rights can merge this in.
Document (or fix) that limit of 127 characters per argument. Also add a check for it here, or the overflow behavior is a potential problem.