New UI for finding/creating rooms (including bridged rooms)

[ara4n]

This is split off from #1882.

@antikewl has provided some designs for finding/creating rooms as per zpl.io/11c9Ws, zpl.io/Z1u6JH8, https://zpl.io/2jFojg and https://zpl.io/2erp6m.

There are some problems here though:

• This makes the room directory incredibly visible when you want to create a room. Psychologically, if your intent is to create a private room (e.g. Vector Design), and you hit the Rooms button, you're currently shown all the directory contents by default - immediately making you think in terms of public free-for-all rooms. The directory also takes a while to load. I am unsure that we want to be showing it by default, but only if the user explicitly says "actually, i want to find a public room to chat in".
• We need a way of filtering the directory to particular remote networks - e.g. "show me available channels on the ribot slack". In future, we will also need the ability to select different directories - e.g. "show me rooms from the arasphere.net Matrix server" or "show me rooms for the Vector team group"
• We need a way to join rooms by alias (currently this is cryptically hidden - if you enter an alias like #matrix:matrix.org into RoomDirectory's input field and hit return, it joins you). Sorry for not spelling this out as a requirement earlier.

I don't have a concrete suggestion here, i'm afraid, but perhaps a page of form...

* [ Create a new room ]
* Join room: [ e.g. #foo:matrix.org........... ]   (
* Search room: [ .............. ]  [ List of directories |v|]  [ Directory ]

[ Search results or directory contents go here ]

...might be sufficient (square brackets indicate form controls), where hitting the Directory would show you the unfiltered directory contents, whereas Search would let you search the directory?

[antikewl]

https://zpl.io/11c9Ws

Rooms default view

https://zpl.io/ZCjdQJ

Rooms search result

https://zpl.io/ZjrXQV

Rooms network select/filter menu

https://zpl.io/Z1RCiSd

Left menu search ("More rooms" opens pre-filled search result above)

https://zpl.io/Z13pkVG

[antikewl]

Revised left navigation

Future room directory screen

[ara4n]

A first pass of this is being implemented in #2178. I'm going to keep this open at lower priority as we will probably need to iterate a bit more post-freeze.

[turt2live]

We've since iterated on the designs for post-1.0. The designs look awesome for Vector, though they are a bit dated now :(