[feature]Multiple use fixer.

Multiple use fixer.
As requested: #140
Actually I cherry-picked this method from UnusedUse (https://github.com/fabpot/PHP-CS-Fixer/pull/471/files).
This method is common for both fixer and do one thing - search for indexes of T_USE tokens which stands for using namespace, not trait or at lambda fuctions ($foo = function () use ($bar) {...}).

Duplicate this code in two fixers is wrong, and since it operates on Tokens collection - I found no better place for it.
You know one?