I18n improvements

There have been many English words not translated yet. I moved them into the localisation file. Furthermore I added a German de.yml file. And there was an error in the configuration Cms::Fortress::Configuration. Eg

    :name => 'pages', :title => 'admin.cms.base.pages'

should have the namespace `comfy.admin.cms.base.pages` for `:title`

I hope the PR is not too big. There are three isolated commits you can cherry-pick. Let me know, if you want me to change anything.

Thanks for this awesome fork of CMS :)