Add support for named launch profiles to quickly switch between settings

[camall3n]

These would be separate from configs. We could call them "profiles" or something similar and then add a --profile option to the launch subcommand.

[camall3n]

Possible workflow:

$ onager profile add myprofile1 --gpus 1 --cpus 4 --mem 16 --duration 02:30:00
$ onager profile add myprofile2 --cpus 2 --mem 64 --duration 01:00:00
$ onager profile list
     profile  options
------------  ----------------------------------------------
  myprofile1  --gpus 1 --cpus 4 --mem 16 --duration 02:30:00
  myprofile2  --cpus 2 --mem 64 --duration 01:00:00

onager launch --profile myprofile1 --jobname some-job