update changelog
update players changelog
add "Defense Capped" col. to terrain table in help page for units

If a unit has a "negative" modifier on one of its terrain defenses,
for the basic terrain defense types that have been discovered and
will be displayed on the current help page, a column will be
generated "Defense Capped" which indicates which terrain types
have the negative modifier. In each row the column contains either
'-' or 'yes'.
add a help topic link from "Defense Cap" col. to terrains section

Added to the topic for that section a brief explanation of mixed
terrains vs basic terrains, "best defense worst movement", and
defense caps.
fix bug in help.cfg wherein list of terrains wasn't generated
Merge branch 'master' of git://github.com/wesnoth/wesnoth
update changelogs