predict method rewritten to use with PredictCollector interface (abstract class)
now face recognizer allow to perform different scenarios of result handling

results in less code and more consistent parameter handling.

It doesn't support thread_local

For some applications it is useful to have an estimate of how uncertain
the specific variable is estimated. This could help to act accordingly
e.g. increase the measurement zone if the current estimate is very
uncertain. 

Fixed warnings for XCode 7.1.1 and cmake 3.3.2, rewrote one method in sliency to avoid clang 7.0.0 crash

According to ISO C++03 14.2/4 it should use the template keyword to fix this => http://stackoverflow.com/a/3786481/724098