Enable optional larger unit output for cli tool

[trent-s]

Currently, susqltop outputs values in Joules and grams.
It would be nice to offer ability to output in larger units.

[trent-s]

Thinking about offering the following modifiers to adjust units for both energy and carbon.

• -k (kilo) to give us kilojoules kilograms
• -m (mega) to give us megajoules and megagrams
• -g (giga) to give us gigajoules and gigagrams

In the event of multiple specifications, the last one has precedence.
In addition to calculation, also update unit displayed in header.
Probably should rewrite to use the getopt command internally.