OCL: minor optimization of cv::moments

**Description:**
* Minor optimization: instead of computations of factor values in kernels, corresponding factors were precomputed and then used in kernel. 

* Extended kernel to binary mode, before that the code was executed on CPU (if flag 'binary' was set).

**Performance report:**
http://ocl.itseez.com/intel/export/perf/pr/2881/report/

check_regression=*OCL*Moments*
build_examples=OFF
test_filter=*OCL*Moments*
test_modules=imgproc