use absolute paths with fullfile function
support more options for mexopencv.make

can specify opencv path, clean mode, dry-run mode, force recompilation,
and ability to pass extra arguments to Unix make
add test target to mexopencv.make to run unittests
edit docs
detect VS2012 as compiler

although not yet officially supported by MATLAB, Windows builds of
OpenCV (v2.4.4) come with a vc11 compiled executables.
check opencv directories exist
ignore more files generated by VS
fix Makefile to clean all mex-files
return parsed arguments as a struct

in addition, explicitly convert them as the expected type
add option to show progressbar during compilation

only for the Windows version
unix makefile uses pkg-config to locate opencv
Merge pull request #53 from amroamroamro/make

Improve compilation script