Basically we were advertising that the source size would be the
size of the track if it hadn't been defined by end user, but since
we started to let scaling happen in the compositor, this is not true
as the source size is now the natural size of the underlying video
stream.
Remove the unit test and reimplemented using a validate scenario which
make the test much simpler to read :=)
Do not list all the possible options in the man page but only the help
options.
This is in order to avoid duplication and prevent the man page from
becoming obsolete in case the options change in the code but do not get
updated in the man page.
https://bugzilla.gnome.org/show_bug.cgi?id=776063
