Create room with customized power levels.

The config.json will have a section called initial state that contains the power levels at which the rooms will be created.

```json
"initial_state": {
"power_levels": {
"events_default": 0,
"users_default": 0,
"state_default": 50,
"events": {
"m.room.avatar": 0,
"m.room.name": 0,
"m.room.topic": 0,
"m.room.message": 0
}
}
}
```

Start with the config.json handling and the room-creation entry point, then trace how the initial_state.power_levels values are read. Done means rooms are created using the configured default and per-event power levels, with the existing room-creation checks still passing.

Written by the indexing model from the issue text.