Parse and store both col align and col width spec for later use

Parse and store both col align and col width spec for later use

* lisp/org-exp.el (org-store-forced-table-alignment): Parse
the column cookie for both alignment and width specification.
Store the resulting value in `org-col-cookies' property.
Retire the previously used `org-forced-aligns' property for
consistency.  Renamed local variable `aligns' to `cookies'.
* lisp/org-html.el (org-format-org-table-html): Use
`org-col-cookies'.  Renamed local variable forced-aligns to
col-cookies.

This is a preparatory patch.  A backend can look at the colwidth
specification and (at it's discretion) use it to control relative
sizes of individual columns in a table.  At this moment, it is unclear
whether the widths used to control the display of table in Org buffer
can be overloaded to also control the formatting of table in a
backend.

Refer following discussion with Matt Price:
http://lists.gnu.org/archive/html/emacs-orgmode/2011-08/msg01053.html