Planet power, nebula timers update

[SirEmi]

SO Main:

Nebula times:
- diminishing nebula for SO Main if entering nebula again in 6h after another nebula has changed from
- minimum nebula changed from 12h to 15h
- decay time from 24h decreased from 4h diminishing to 3h diminishing

Planet power:
- planets colonists and credits are counted into the total power of a commander
- credits in the mining facilities are counted into the toal power of a commander
  Beware, if you have a low power and no mothership assets and only planet assets, your mothership may be at a high risk in case of counters and you will enter nebula harder (20% damage to total power in the last 24h), due to the added power from the planets.