More sensible defaults and allow for overriding. Also make PDB installation
optional on Windows if RelWithDebInfo isn't the build type being used.
CMAKE_INSTALL_PREFIX defaults to GStreamer install location on Windows and
/usr/lib on other platforms.
PLUGIN_INSTALL_DIR defaults to CMAKE_INSTALL_PREFIX/gstreamer-1.0
LIBRARY_INSTALL_DIR defaults to CMAKE_INSTALL_PREFIX/
PDB_INSTALL_DIR defaults to CMAKE_INSTALL_PREFIX/
This is a convenience function to avoid using a capssetter when we want to treat
Bayer as gray. In the future we can add properties to balance each element of the
CFA.
Note there's a bug with the in-place transform, so currently a memcpy is being used.
