Add customize subdirectory to ./run script.

This fixes commit 2b208d84db080659badbb70044497aae040592e7.
customize: Add various options from virt-builder.

This adds the following options to virt-customize:

  --attach
  --attach-format
  -m / --memsize
  --network / --no-network
  --smp

This fixes commit 2b208d84db080659badbb70044497aae040592e7.
customize: Rename main.ml to customize_main.ml.

The OCaml compiler isn't happy when two modules have the same name in
different directories.  Since customize/ contains a library of modules
used in other directories, and since those directories may have
main.ml files too, we need to rename 'customize/main.ml' to
'customize/customize_main.ml'.