fixed some compile warnings in dnn & protobuf; improved convolution speed

fixed some compile warnings in dnn & protobuf; improved convolution layer performance when blas is not available by parallelizing gemmCPU() function in dnn

* Fix kcfTracker when called from Python bindings. The variable boundingBox in updateImpl when called from Python is initialized with 0s and it needs to be updated with the tracker state.

* Fix to return the bbox correctly in the first frame in Python

optflow: updated motempl.py sample

fix modules deps

* Add bilateral texture filter

* Change tab to space

Fixed some inconsistencies in interfaces of different white balance algorithms and improved
the documentation a bit. Also added an option of loading a model during runtime in the
learning-based white balance algorithm. Added a simple tutorial describing how to train a
white balance model.