Thanks Anssi Kääriäinen for help.

Thanks Maxime Lorant for the report and Tim Graham for suggesting
the improved comment.

jQuery cookie is no longer maintained in favor of the JavaScript
cookie library. This also removes the jQuery dependency.

The test is a regression for refs #4740 to show that the original
fix of GEOSIndexError is no longer needed.

Thanks Florian Apolloner and Carl Meyer for review.

This is a security fix.

Thanks Carl Meyer for the report and Tim Graham for the review.

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 "%%".