Use likelySubtags to instantiate a locale id from it's short form

Use likelySubtags to instantiate a locale id from it's short form

...just like described in http://www.unicode.org/reports/tr35/#Likely_Subtags.
This is much more effective than current "guessing" algorithm
+ makes it possible to instantiate a locale by the script or territory code only.

Change-Id: I674f8476e65b01c56960b6e83a1a346df0715274
Reviewed-by: Lars Knoll <lars.knoll@digia.com>