Improve game starter args

[merfolk]

Besides refactoring, at least these changes are included:

• --human protoss argument removed and merged into --player1 human.protoss
• Fix -release to -r
• Fix -map to --map
• Add -m along with --map
• State defaults of each parameter in help text
• Sort available maps and bots in helpo text

[merfolk]

When this PR is merged, I would like to add different usages scenarios into Running Games wiki page:

Bot vs. bot

Zerg 12 pool against protoss proxy zealot rush on random map.

py run_custom.py -p1 12pool -p2 zealot 

Bot vs. in-game AI

Zerg 12 pool against in-game AI.

py run_custom.py -p1 12pool -p2 ai.terran.hard

Human vs. bot

Human terran against cannon rush on on AcolyteLE map.

py run_custom.py -p1 human.terran -p2 cannonrush --map AcolyteLE