Add memory to Info object

[johrstrom]

It's clear we need the Info objects to return memory information about the job.

Here are some thoughts I have

• units should be bytes so upper layers like OOD can cast and format as they like.
• We should start with total memory, I could be convinced for memory per node, but I kinda feel like we should just defer that until we need it to avoid a YAGNI situation.

[moffatsadeghi]

This has been dropped from 4.1, unfortunately, due to conflicting needs for 4.1.