[tlbuild] List of packages included in tetex3

[Karl Berry]

    The tetex-scheme coming from the tl-installer gives several hundrets of 
    megabytes(as tar.xz), the old tetex3 is about 40mb(tar.xz) without doc 

If you come up with a list of packages, please let me know.  I could
change scheme-tetex to explicitly list more packages instead of
collections.  One major difference is that luatex did not exist in
tetex, but it is required now for (most) things to work.  So expecting
no growth at all isn't realistic.

collection-pictures is one that has had numerous additions.  -k