Add column with showing per-process unique memory usage value (calculate RES - SHR)

[MurzNN]

Very often we need to know, how much unique RAM used by specific process. The unique memory usage of separate process can be easily calculated manually via RES - SHR formula (or VIRT - SHR - SWAP?), but online calculating manually for each row is too hard task.

For solve this problem, will be good to add "Process unique memory" (PUM?) that will calculate this automatically, alsy with ability to sort process list by this value. What do you think about this idea?