updated Retina module code for more flexible parallelisation : TBB parallel for loops are replaced by opencv parallel_for_ wrapper... compile error corrected

updated code for more flexible parallelisation : TBB parallel for loops are replaced by opencv parallel_for_ wrapper

+ Fixed warnings
+ Add new function calcOpticalFlow with smaller number of arguments
+ Add asserts to algorithm and remove 'exit(1)'

+ New format for flow data - CV_32C2
+ Memory optimization
+ Cross Bilateral Filter optimization
+ Minor optimizations
+ Sample for calcOpticalFlowSF improved

"SimpleFlow" optical flow estimation algorithm (GSoC project) declaration in includes, implementation, usage example, test

add getoclcontext and getoclcommandqueue so that other opencl program can interactive with opencv ocl module
correct haar test cases
add face detection sample

add OCL 1.2 feature for setTo
bug fix of integral
replace the error code -217 with suitable MACRO
simplify tests, no need apply a new context for each test case
add more control for tests in utility.hpp