Allow Player@X functionality for more script related functions

Player@X allows trigger actions needing a country as a parameter to directly affect a players side rather than it depending on what country they are playing as. Unfortunately it doesn't work for events the same way, so you can't detect when a player does something to reward/punish them specifically or anyone else not them. Similarly it also doesn't work as a trigger or teamtype owner which are needed for some trigger functionality to affect a specific player.

Expanded player@x functionality would allow new game modes based on customised maps in the same way the assault game mode works. For example it would be possible to create a version of the cut "siege" game mode.