[O] split ascii-plot package into pure ascii & unicode

[Thierry Banel]

I removed unicodes characters from the orgtbl-ascii-plot package.
This makes it safe for Org exporters.
The unicode version is kept separatly, as an extension example.

The file (code & doc) is here
http://orgmode.org/worg/org-contrib/orgtbl-ascii-plot.html

| values | ascii plot   |
|--------+--------------|
|     25 | WWWWWW.      |
|     16 | WWWH         |
|      9 | WW:          |
|      4 | H            |
|      1 | :            |
|      0 |              |
|      1 | :            |
|      4 | H            |
|      9 | WW:          |
|     16 | WWWH         |
|     25 | WWWWWW.      |
|     36 | WWWWWWWWV    |
|     49 | WWWWWWWWWWWW |
#+TBLFM: $2='(orgtbl-ascii-draw $1 0 49 12)

By the way, the FSF acknowleged my copyright assignment
(the whole process took 3 weeks for me).

Have fun
Thierry