wren (control script): Reformat usage table with separate RAM and Swap

[codewithmichael]

• Addresses #25 (Add optional RAM and Swap entries to "wren usage")
• Potential merge conflict #29 (Option to disable active data file system)
• Potential merge conflict #30 (save.sh + wren: Add --no-snapshot option)

This commit reformats the wren usage output table with [STORAGE] and [MEMORY] headers and subdivides the previous memory line into ram, swap, and total. The line is still labeled memory if wren usage memory is called.

Additionally, the unallocated header has been shortened to unalloc in human readable mode and the all subcommand will additionally display the active or save lines even if they are not currently applicable.

Sample Output:

user@computer:~$ sudo wren usage -h
           total    used    free  unalloc
[STORAGE]
active:     1.0G    8.8M  885.9M        -
device:     5.9G    2.9G    2.6G        -
[MEMORY]
ram:        3.9G    1.3G    2.5G        -
swap:         0B      0B      0B        -
total:      3.9G    1.3G    2.5G     1.7G

[codewithmichael]

Note: This is likely to cause a merge conflict with PR #30.

[codewithmichael]

It appears that when a save file is used directly, wren usage correctly hides the "unallocated" header and subsequent fields except for the memory/total line. On that line the field is still hard coded to '-' instead of using "$unallocated_unused" as is done everywhere else.

I will make this correction as part of the merge.