Fix #2895: Problems with translations in plugins (part 2)

In extensions created using the current templates `*.mo` files (compiled
translations) are not picked up during packaging.

The fix is to include these files via the `MANIFEST.in` file and to
update the template accordingly.

ckan/pastertemplates/template/MANIFEST.in_tmpl

@@ -1,2 +1,2 @@
 include README.rst
-recursive-include ckanext/{{ project_shortname }} *.html *.json *.js *.less *.css
+recursive-include ckanext/{{ project_shortname }} *.html *.json *.js *.less *.css *.mo