Feature: rework in-game Online Players GUI

The GUI now more clearly shows some basic information about the
server you joined, your client name (and the ability to change it),
and what players are in which company.

It also contains useful buttons to press to join companies, chat
with other people, and for admins to kick/ban people.

Additionally, renamed "advertised" to "visibility"; this has to
do with future additions, but also because it is more clear in
wording.

media/baseset/openttd/openttdgui.nfo

@@ -4,7 +4,7 @@
 // See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 //
    -1 * 0	 0C "OpenTTD GUI graphics"
-   -1 * 3	 05 15 \b 186 // OPENTTD_SPRITE_COUNT
+   -1 * 3	 05 15 \b 189 // OPENTTD_SPRITE_COUNT
    -1 sprites/openttdgui.png 8bpp  66    8  64  31 -31   7 normal
    -1 sprites/openttdgui.png 8bpp 146    8  64  31 -31   7 normal
    -1 sprites/openttdgui.png 8bpp 226    8  64  31 -31   7 normal
@@ -191,3 +191,6 @@
    -1 sprites/openttdgui_convert_tram.png 8bpp  24   0  32  32   0   0 normal
    -1 sprites/openttdgui.png 8bpp 513  440  10  10   0   0 normal
    -1 sprites/openttdgui.png 8bpp 526  440  10  10   0   0 normal
+   -1 sprites/openttdgui.png 8bpp 539  440  12  10   0   0 normal
+   -1 sprites/openttdgui.png 8bpp 553  440  12  10   0   0 normal
+   -1 sprites/openttdgui.png 8bpp 567  440  12  10   0   0 normal