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

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. 

Added the "How to write a tutorial for OpenCV?" tutorial. Made some corrections to the feature2D TOC tree. Small visual improvements for the video-write.rst file. Deleted a definition file that served no purpose.

Added to the tutorials the "Support Vector Machines for Non-Linearly Separable Data" contributed by Fernando Iglesias García. Corrected a mistake in the gpu-basics-similarity.rst file. 

Added the "Similarity check (PNSR and SSIM) on the GPU" tutorial. Corrected an highgui TOC tree mistake.

Added the How to create videos with OpenCV Tutorial. Made some corrections to the feature2d, to get rid of some documentation build errors. 

* Fixed display of struct and class definitions (except classes with base class specified).
* Fixed formatting and referencing errors in several documentation files.

Added tutorial for features2d using homography to find a planar object (Based on the well known find_obj.cpp

Added reference to Nvidia TADP into Android tutorial; refactored both Android tutorials; fixed some rst warnings

Added the tutorial "Using OpenCV Android binary package to compile applications, which use OpenCV from native level".

Added the "Mask operations on matrices" tutorial (with its sample). Plus modified some other core tutorials.

Added Fernandos first tutorial regarding SVMs. Extended the global links (conf.py). Corrected the author names. Minor modification to the dft tutorial.