Remove load/save list buttons from the mod manager

The feature these buttons provide doesn't exist (they have no click listeners,
they're just two disabled buttons)

Closes #258
Fix various tooltips

Closes #259
Start setting the description
Condense flag designation logic
Clean up the rules display
Default map version to 1

Closes #261
Repair null-statistic observers
Properly center text on load game button
Don't show load game button in multiplayer mode

Closes #250
Attempt at preventing connectivity screen

People exiting with ALT+F4 cause games to hang for a minute or so until a
timeout is reached and everyone boots them.

This is intensely annoying. The problem seems not to occur when a player
gracefully quits from the menu. This patch is a ridiculous hack that causes the
"graceful exit" code path to execute when a user simply ALT+F4s the game in
rage.

Note from Sheeo:
> All right, merging this since it ought to be harmless. We'll collect
> anecdotes during the lifetime of 3639 to see if it needs to go in 3640 or
> not.

Closes #248
Make the large map preview less pixelated

... And stop rebuilding it in UpdateGame!
Revert "Add easter-egg props"

This reverts commit bf53f5ada048a10fc638be90a5fe6ce0730ed470.
Revert "Show overflow from allies"

This reverts the following commits:

- 9f50e22a43352d751cc097efa5baa3ecef19d21e
- 8bf304ea62d4f987c4e91dab37a2b972cb03015e
- f4ee3a5dea79e3a4a9cbe92ace34c6e807ecb4dd
- 2b257466f047dc322558bb08a02a622acb247916
- bca83737c6bae3f6f507692b09e8bc1cf5d98db7
- 7984dc5d7012c17f549d8fa2fc9a31126c5228a1
- 702adfde6dc2931855ceedcba34b7c78da090894

These are being postponed for patch 3640, and a time when they are more stable
and agreed upon.
Revert "Prepend clan tags to requested player name"

This reverts commit 74c48dcbdddd6fb53df70923cb6df8c3829adf4c.
Update changelog for 3639/2.6.0
Make the Lobby Preset button description work
Grammatical cleanup of the mod manager
Change TAB to spaces in ModsManager.lua
Clean up comments and whitespace, fix syntax error
Visual changes to the English in mod manager

Closes #268