CRM-13584: installer template.css: cleanup CSS, set max-width of body to 1200px.
CRM-13584: make it possible to localise the CiviCRM installer. Moves the language option to the top, and adds more help text on how to localize. (NB: some ts() were added to the strings, but not all yet).
Merge pull request #1795 from mlutfy/master-crm13584-instali18n

CRM-13584: support i18n in the installer script