Draft: Give Game Masters ability to modify current boss point gain rate

This is at discussion stage and entirely untested.

The idea is to give GM the ability to modify boss point gain rates for all REPEATABLE quests. One time quest should probably be left untouched to prevent players from waiting with their quests unfinished until BP boost event, as has happened with certain large xp quests in the past.

Undecided/unsolved problems:

1. add command to modify rates? Or is @setvar sufficient?
2. add an @allrates or similar wrapper around @rates that notifies about raised BP rates. Or decorate @rates itself (how?).
3. How many more quests to add? Current: crypt generals, Candor, Illia, Cindy(2nd+).