fixed bug in gpu::matchTemplate (added normalization routine to make the GPU version consistent with the CPU one), added test cases from the ticket #1341

2) device layer utility

modified highgui and ts modules and cmakelists for ios cross-compiling, added ios toolchains, added ios build tutorial

all video processing samples use camera as default source (and fallback to synth in case of capture error)

Added the "Camera calibration With OpenCV" tutorial. Extended with a few global links the conf.py file. Corrected an error in the linux_install.rst and one in the cascade_classifier.rst file. 

updated retina modules : minor misakes correction & changed pixel format to float instead of double to keep some memory, precision is almost sufficient, check for residual mistakes

updated retina modules : minor misakes correction & changed pixel format to float instead of double to keep some memory, precision is almost sufficient, check for residual mistakes