Make sure Atom feeds are served with content type application/atom+xml

Fixes #961
Restore tabs to keep string for translation the same as previously
Update of strings for translation by running rake gettext:store_model_attributes, and rake gettext:find
Merge branch 'rails-3-develop' into release/0.11
Add some upgrade notes for the 0.11 release.
Add note about config/httpd.conf
Fix typo.
Merge branch 'feed-content-type' into rails-3-develop
Merge branch 'rails-3-develop' into release/0.11
Merge branch 'release/0.11' into wdtk-upgrade-test