Sample C++ code for detecting facial features

Added sample code for facial feature detection
C++ code for detecting faces and facial features (eyes, nose and mouth)
using Haarcascade classifiers has been added to the samples/cpp
directory.

Fixed some errors
Fixed some compilation errors and ran local tests on code.

Fixed whitespace errors and warnings.

Fixed the issues raised in the pull request
Changed an exit(1) statement to return 1 and modified the code to take
all haarcascade files as input so that running the binary becomes
location invariant.
Merge remote-tracking branch 'opencv-samyak/master'