Remove the GstVideoPlane structure and move the fields directly into the
GstVideoInfo structure. This makes things a little easier to read and also makes
it more likely that we can pass the stride array to external libraries.
Add GstVideoFlags similar to the flags on the metadata. The idea is to replace
the metadata flags with the GstVideoFlags.
Move VideoPlane to video.h, it contains the information for a plane.
Add GstVideoInfo structure that holds the current configuration of a video
format.
Add methods to parse caps into GstVideoInfo.
