Python typdef fixed. Reverted the example to MOG2. Not time to make the command line switch for now.

ReST directive was used. Also fixed some other ReST directives that were
not correct and removed some warnings during buildbot checks.

- Used lunix style slashes - works on most systems
- Removed all trailing whitespaces

This makes arguments of type InputOutputArray required in python unless they
have a default value in C++.

As result following python functions changes signatures in non-trivial way:

* calcOpticalFlowFarneback
* calcOpticalFlowPyrLK
* calibrateCamera
* findContours
* findTransformECC
* floodFill
* kmeans
* PCACompute
* stereoCalibrate

And the following functions become return their modified inputs as a return
value:

* accumulate
* accumulateProduct
* accumulateSquare
* accumulateWeighted
* circle
* completeSymm
* cornerSubPix
* drawChessboardCorners
* drawContours
* drawDataMatrixCodes
* ellipse
* fillConvexPoly
* fillPoly
* filterSpeckles
* grabCut
* insertChannel
* line
* patchNaNs
* polylines
* randn
* randShuffle
* randu
* rectangle
* setIdentity
* updateMotionHistory
* validateDisparity
* watershed

e.g. <opencv2/core/core.hpp> become <opencv2/core.hpp>

Also renamed <opencv2/core/opengl_interop.hpp> to <opencv2/core/opengl.hpp>

Evangelidis, G.D. and Psarakis E.Z. "Parametric Image Alignment using Enhanced
Correlation Coefficient Maximization", IEEE Transactions on PAMI, vol. 32, no.
10, 2008

* added DenseOpticalFlow interface
* moved OpticalFlowDual_TVL1 to src folder

Invalid links and refences fixed.
SpaeseMat class documentation updated.

All errors were found by doc/check_docs2.py

All errors were found by doc/check_docs2.py

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

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

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

declaration in includes, implementation, usage example, test