doc-rst: customize RTD theme, table & full width

doc-rst: customize RTD theme, table & full width

The default table layout of the RTD theme does not fit for vast tables,
like the ones we have in the linux_tv project. This has been discussed
on the ML [1].

The RTD theme is a two column layout, with a navigation column on the
left and a content column on the right:

content column

 RTD theme's default is 800px as max width for the content, but we have
 tables with tons of columns, which need the full width of the
 view-port (BTW: *full width* is what DocBook's HTML is).

table

   - sequences of whitespace should collapse into a single whitespace.
   - make the overflow auto (scrollbar if needed)
   - align caption "left" ("center" is unsuitable on vast tables)

[1] http://article.gmane.org/gmane.linux.kernel/2216509

Signed-off-by: Markus Heiser <markus.heiser@darmarIT.de>