Miscellaneous fixes to strings found during i18n work.
Minor tweaks found during i18n work.
Use the same marker everywhere for translator comments.
Mark XModule strings for i18n
Fixes to Translator comments found while debugging the i18n pipeline.
Lorem is now fancy, and HTML tags are recognized with single-quote attributes.
Use ddt to separate test cases into tests.
Fix plurals; validate downloaded .po files.

Fix the handling of plurals so that dummy files pass the msgfmt checks.
test_validate.py now doesn't just run msgfmt -c, it also examine the
results.