Refactored tests to use a sample project.
Updated extraction:
* Removed special handling of single percent signs.
* When extracting messages from template text, doubled all percent signs
so they are not interpreted by gettext as string format flags. All
strings extracted by gettext, if containing a percent sign, will now
be labeled "#, python-format".
Updated translation:
* Used "%%" for "%" in template text before calling gettext.
* Updated {% trans %} rendering to restore "%" from "%%".
Instead of crashing with a CommandError, now a non-writable location
of mo files will only make compilemessages complain and continue.
Thanks Ramiro Morales for the review.
Removed multiple locales separated by commas variation (that wasn't
working as documented) in favor of simply allowing use of the
``--locale``/``-l`` options more than once for ``makemessages`` and
``compilemessages``.
Thanks Romain Beylerian for the report and Claude, Simon for their help.
8750296918 from stable/1.6.x.
