MatSize::operator()() supports only 2-d matrices.

The following data types for attributes are implemented:
 - int
 - double
 - cv::String
 - cv::InputArray

- Fixed a typo in the help text
- Fixed a typo in a comment line

 - Some test cases are added
 - Two tutorials are written to show how to use it.

to prevent console spam. only outputs errors/ warnings now.