Documentation: Provide default values for version/release ...

Provide default values for version/release so it would be possible to
run Sphinx outside of the build system. Useful for rst-sphinx backend
of flycheck in Emacs, for example.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Documentation: don't highlight literal blocks as shell script ...

There are multiple cases in the documentation where literal blocks are
used for literal, preformatted text. Although it is possible to use
`.. code-block: none` in these cases instead of literal `::` blocks,
follow the principle of least surprise and don't apply any syntax
highlighting at all for literal blocks.

Signed-off-by: Roland Hieber <r.hieber@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Documentation: change default highlight language to shell ...

There are many places where sphinx complains that blocks cannot
be hilghlighted in 'c' and in fact I am not aware of any C code
snippets in the documentation, so change the default highlighting
style to shell which fits our needs much better. With this we
get rid of many warnings while building the documentation.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Documentation: Add new sphinxs docs ...

This is a rewrite of the Documentation in reStructuredText format using
Sphinx as build system, see http://sphinx-doc.org/.

The documentation is built into static html pages with 'make docs'.
The pages can be found under Documentation/html after building.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>