Added optional reason to the ignore feature.

In multiplayer, this supports players to associate a reason with ignored users that is displayed with the ignored username. Resolves http://wiki.wesnoth.org/EasyCoding#Add_possibility_to_give_reason_for_.22ignore.22.
Added timestamps in Chatlog

It was a little odd that timestamps checkbox in Preferences affected
only regular chat messages, but not the chatlog, so I decided to add
timestamps into the chatlog.

I hate to use `const_cast` to add a timestamp to a received message, so
if someone knows a better solution, don't hesitate to mention it.
Improved friends storage system to store "acquaintances" as separate children.

The current attributes are status (either friend or ignore), the nickname, and any attached notes.
Don't need to escape the reason anymore with new storage system.
Added notes for friends.
Fix a clang compile error.
Copy all of the slider states when resizing.
Fix the "End Turn"/"End Scenario" button states, a patch from
thunderstruck
Fix the menu entry "End Turn" not switching to "End Scenario".
Mention the editor gui's overhaul in the changelogs.
pot-update and regenerated doc files
bumped version to 1.11.3
fixed changelog reference to point to github
Recalculate labels and button states after zooming with the slider.
Clear the sliders on resize to avoid duplicating them.
applied utiles/wesnoth-optipng on images/

Overall statistics (only for files with a smaller recompressed size):
  Original size: 423 KiB on 192 files
 Optimized size: 216 KiB
   Total saving: 207 KiB = 48% decrease
applied utiles/wesnoth-optipng on data/

Overall statistics (only for files with a smaller recompressed size):
  Original size: 276 KiB on 14 files
 Optimized size: 226 KiB
   Total saving: 50 KiB = 18% decrease
Replaced png files that had obtained an embedded ICC profile, which was causing error messages
applied utiles/wesnoth-optipng on the latest images from Lord_Bob
Fix missing icon overlays.