Remove verbose state events from the timeline

[jmartinesp]

When creating a room, we can see at least 7 state events being added to the timeline:

• Who created the room (m.room.create).
• The same person joining the room (m.room.member with membership join).
• The room power levels being set (m.room.power_levels).
• The room join rules being set up (m.room.join_rules).
• The room history visibility being set up (m.room.history_visibility).
• The room guest access being set up (m.room.guest_access).
• If encryption is enabled or disabled (m.room.encryption).

Plus any invites.

From those, we only want to display:

• Who created the room.
• Who joined the room.
• If encryption is enabled.
• The invites.

So we need to filter out the rest of the events from the timeline. Following iOS' implementation, this removal should be done globally in the timeline, not just for the few first items.