remove opencv1 dependencies.

bgslib now compiles on Linux systems without libcv-dev installed.
Almost all calls and incudes have been ported to opencv2, some are
still used via opencv2/legacy/compat.hpp (e.g. cvFillImage).
Hope I got everything fine also for mingw since I removed two
mingw related defines.
I don't have a mingw install to check it against.
MSVC 2010 is fine with the provided project file.