Smile detector

Smile detector based on a new smile cascade.
Added with sample smiledetect.cpp which also measures smile intensity.

Based on:

Smile Detection for User Interfaces. O. Déniz, M. Castrillón, J. Lorenzo, L. Antón, G. Bueno. 4th International Symposium on Visual Computing (ISVC08), Las Vegas, USA, Dec 2008.