Sorting by process name (PROC column), or grouping by pid of parent

Right now `numatop` shows the following propmt
```
Hotkey for sorting: 1(RMA), 2(LMA), 3(RMA/LMA), 4(CPI), 5(CPU%%)
```
However, it would be useful to have an ability to sort by PROC column as well.

Another useful feature could be grouping by process subtree starting from selected process, or limiting view to include only this subtree (e.g., it could be implemented as `-p PID` command line flag). Most multiprocess applications have a single "host" process which is direct or indirect parent of all computational processes, so it would allow to analyze behavior of all processes belonging to the certain computational job even if these processes have different process names.