Enable lobby chat in gamesetup/session

[Imarok]

There should be a way to acces the lobby chat out of gamesetup.

Maybe with two tabs to switch between the gamesetup and the lobby chat. (A third tab could be added for the content of the "More Options" button, which is growing more and more)

[elexis]

Should also be possible to access the lobby while in a running game.

(Dupe at #4483)

[elexis]

In 20110:

Move prelobby files to a separate directory (to prepare splitting the lobby code into several files).

Refs #4106, D817

[elexis]

In 20111:

Move lobby panels to custom file, so that they could be shown in a dialog as well.

Refs #4106, D817
Patch By: fpre / ffffffff

[elexis]

In 20872:

Allow the JS GUI to find out if the lobby client is currently disconnected.

Differential Revision: ​https://code.wildfiregames.com/D1224
Patch By: fpre / ffffffff
Refs #4106, D817

[elexis]

In r20886
Enable players to open the lobby as a dialog in the gamesetup, running games and the summary screen.

Differential Revision: ​​https://code.wildfiregames.com/D817
Patch By: fpre / ffffffff
Fixes #4106

[elexis]

The two XML files created in r20111 are useless now, but merging them into a single file isn't really adding a benefit now either.

[elexis]

In 21263:

Add the lobby button to the summary screen.

Patch By: fpre / ffffffff
Differential Revision: ​https://code.wildfiregames.com/D1272
Refs #4106

[elexis]

In 21345:

Fix missing right-alignment of lobby icon in the summary screen following rP21263, refs #4106.