Store full player profiles in F-key templates

[dgruss]

Fixes #137. Also fixes #280.
This PR extends the existing F1-F12 player template shortcuts so they handle the full player setup, not just the name.

• save/load player name, color, avatar, and difficulty in F-key templates
• allow F1-F12 and Shift+F1-F12 anywhere on the player setup screen
• keep focus on the current control when saving/loading templates
• show a short top-right saved/loaded indicator
• refresh the color selector after loading a template so it shows the restored color
• update the player setup help screen wording from player names to player profiles
• F-keys in party mode are still name only