Add short flag counterparts

[Neved4]

Short flags enhance brevity and conciseness.
Currently, some options lack equivalent short flags to invoke them:

• -w, --warmup
• -m, --min-runs
• -M, --max-runs
• -r, --runs
• -s, --setup
• -p, --prepare
• -c, --cleanup
• -P, --parameter-scan
• -D, --parameter-step-size
• -L, --parameter-list
• -S, --shell
• -N, (alias for '--shell=none')
• -i, --ignore-failure
• -l, --style
• -t, --sort
• -u, --time-unit
• -d, --show-output
• -O, --output
• -I, --input
• -n, --command-name
• -h, --help
• -V, --version

Since --export variants lend themselves to further discussion they are tracked in #691

[sharkdp]

Missing short options in the CLI are not a matter of neglect. They were left out because those options were not considered to be used frequently. Out of the ones listed, only --show-output is something that I personally use frequently. What do others think?