SotA: Set up for translations

This adds an initial pot-file as well as the three pre-existing translations:
    Hungarian, Japanese, Russian

I wasn't sure what to do about translations that don't yet exist, but the
"scons pot-update" target seems to fail if they're missing, so I've
created blank placeholder files for them.

po/wesnoth-sota/FINDCFG

@@ -0,0 +1,2 @@
+find data/campaigns/Secrets_of_the_Ancients -name '*.cfg' -print
+find data/campaigns/Secrets_of_the_Ancients -name '*.lua' -print

po/wesnoth-sota/LINGUAS

@@ -0,0 +1 @@
+af ang ang@latin ar ast bg ca ca_ES@valencia cs da de el en_GB en@shaw es eo et eu fi fr fur_IT ga gd gl he hr hu id is it ja ko la lt lv mk mr nl nb_NO pl pt pt_BR racv ro ru sk sl sr sr@ijekavian sr@ijekavianlatin sr@latin sv tl tr uk vi zh_CN zh_TW

po/wesnoth-sota/Makevars

@@ -0,0 +1,41 @@
+# Makefile variables for PO directory in any package using GNU gettext.
+
+# Usually the message domain is the same as the package name.
+DOMAIN = wesnoth-sota
+
+# These two variables depend on the location of this directory.
+subdir = po/$(DOMAIN)
+top_builddir = ../..
+
+# These options get passed to xgettext.
+XGETTEXT_OPTIONS = --from-code=UTF-8 --sort-by-file --keyword=sgettext --keyword=vgettext --keyword=_n:1,2 --keyword=sngettext:1,2 --keyword=vngettext:1,2 --add-comments=TRANSLATORS:
+
+# This is the copyright holder that gets inserted into the header of the
+# $(DOMAIN).pot file.  Set this to the copyright holder of the surrounding
+# package.  (Note that the msgstr strings, extracted from the package's
+# sources, belong to the copyright holder of the package.)  Translators are
+# expected to transfer the copyright for their translations to this person
+# or entity, or to disclaim their copyright.  The empty string stands for
+# the public domain; in this case the translators are expected to disclaim
+# their copyright.
+COPYRIGHT_HOLDER = Wesnoth development team
+
+# This is the email address or URL to which the translators shall report
+# bugs in the untranslated strings:
+# - Strings which are not entire sentences, see the maintainer guidelines
+#   in the GNU gettext documentation, section 'Preparing Strings'.
+# - Strings which use unclear terms or require additional context to be
+#   understood.
+# - Strings which make invalid assumptions about notation of date, time or
+#   money.
+# - Pluralisation problems.
+# - Incorrect English spelling.
+# - Incorrect formatting.
+# It can be your email address, or a mailing list address where translators
+# can write to without being subscribed, or the URL of a web page through
+# which the translators can contact you.
+MSGID_BUGS_ADDRESS =http://bugs.wesnoth.org/
+
+# This is the list of locale categories, beyond LC_MESSAGES, for which the
+# message catalogs shall be used.  It is usually empty.
+EXTRA_LOCALE_CATEGORIES =