Explore and document --bench argument pattern

[CodyCBakerPhD]

requires #3

With respect to

• child classes of a common benchmark
• 'pretty name' aliases

Both to make it easier to run only a handful of tests, such as 'newer' tests, etc.

also the --skip-existing type flags ASV supports so that a user can pause/resume the running of the suite in a sense

[CodyCBakerPhD]

This has been documented: it's actually pretty restrictive in its use. Needs to be exact benchmark file name and then class name, function name, etc