global i18n : add plantlife_i18n mod

idea taken from homedecor_modpack and its homedecor_i18n
all translated mods have a new dependency : plantlife_i18n
translations are stored in po/pot file : one file for all mods

added french translation (almost complete)
transfered de/es/tr/pt translations to corresponding .po file
(only for some mods, unfortunately translations are incomplete)

plantlife_i18n/tools/updatepo.sh

@@ -0,0 +1,24 @@
+#! /bin/bash
+
+# To create a new translation:
+#   msginit --locale=ll_CC -o locale/ll_CC.po -i locale/template.pot
+
+cd "$(dirname "${BASH_SOURCE[0]}")/..";
+
+# Extract translatable strings.
+xgettext --from-code=UTF-8 \
+		--language=Lua \
+		--sort-by-file \
+		--keyword=S \
+		--keyword=NS:1,2 \
+		--keyword=N_ \
+		--add-comments='Translators:' \
+		--add-location=file \
+		-o locale/template.pot \
+		$(find .. -name '*.lua')
+
+# Update translations.
+find locale -name '*.po' | while read -r file; do
+	echo $file
+	msgmerge --update $file locale/template.pot;
+done