Fix bug 1008698 and bug 777434 - Translation page improvements

Fix bug 1008698 - Add source code view for original article on translation page

Fix bug 777434 - Add a togglable one column editing mode on translation page

Change button names and position on translation page

Fix approved content margin on translation page

Update approved content source to use content_cleaned on translation page

Fix more nits
Merge pull request #2580 from iakshay/translation-source

Fix bug 1008698 - Add source code view for original article on translation page