[FIX] I18N: take new 'navigator.languages' into account, if available

Chrome recently implemented the new navigator.languages attribute as
proposed by the W3C HTML working group
(http://www.w3.org/html/wg/drafts/html/master/webappapis.html#dom-navigator-languages).
Additionally, around Chrome 38, the semantics of navigator.language
changed. It now reflects the Chrome installation language and not the preferred language of the user, as before.

As a result, SAPUI5's Configuration.getLanguage() also returns the Chrome
installation language when running on the newest Chrome version.

With this change, the first language in navigator.languages (if defined)
is assumed to be the user's preferred language. In browsers that don't
implement navigator.languages, the same attributes as before are queried
(navigator.language, navigator.userLanguage, navigator.brwoserLanguage,
in that order).

Note: In future versions, the full navigator.languages array might be
used as an alternative fallback chain. For now, the documented fallback
of Configuration.getLanguage() remains active.

Change-Id: I641feed3ff4d805752c1c419f861b12aa9b6c965
Merge "[FIX] I18N: take new 'navigator.languages' into account, if available"