Fix people section DropTarget and refactor Rooms

- Set the verb for the people section to "tag as direct chat". This requires some CSS modifications to Riot because it's a long bit of text relative to, say, "demote".
 - Because it's quite useful to be able to set the DM status of a room with just a boolean, add a convenience function for guessing a DM member and setting the DM flag on that room with the resulting member.

src/components/views/rooms/RoomList.js

@@ -485,6 +485,8 @@ module.exports = React.createClass({
 
                 <RoomSubList list={ self.state.lists['im.vector.fake.direct'] }
                              label="People"
+                             tagName="im.vector.fake.direct"
+                             verb="tag direct chat"
                              editable={ true }
                              order="recent"
                              selectedRoom={ self.props.selectedRoom }