Testing translations in mailgw.py, update translations, i18n improved

i18n.py: translation objects get a _file which is the file that catalog
         was loaded from. Useful for debugging.

mailgw.py: fix code to include roundup.i18n and invoke propert method.

GNUMakefile: added roundup.pot target. Also building roundup.pot sets
             the release version and product code in roundup.pot.
             Release version from roundup.__init__.py.

merged roundup.pot changes into all *.po files. Not sure if the
   version info in the headers of the .po files is supposed to be
   updated to match roundup.pot or not.

test_mailgw.py: test cases for en and de translations tested. Not sure
   why I neede to set roundupdb._ and mailgw._, but followed setUp
   method code and it worked.

Author: rouilj

locale/GNUmakefile

@@ -48,7 +48,11 @@ template:
 	  ../share/roundup/templates/devel/html/*.html \
 	  ../share/roundup/templates/minimal/html/*.html \
 	  ../share/roundup/templates/responsive/html/*.html
+	VERSION="`sed -ne \"/__version__/s/.*'\(.*\)'.*/\1/p\" \
+	      ../build/lib/roundup/__init__.py`"; \
 	${XGETTEXT} -j -w 80 -F \
+	  --package-name=Roundup \
+	  --package-version=$$VERSION \
 	  [email protected] \
 	  --copyright-holder="See Roundup README.txt" \
 	  -o $(TEMPLATE) $(SOURCES)
@@ -69,3 +73,5 @@ diff:
 
 %.mo: %.po
 	${MSGFMT} --statistics -o $@ $<
+
+roundup.pot: template