Documentation: Rework docs.rst into introduction.rst

docs.rst is the landing page for the documentation from the libcamera
website, but isn't particularly introductory. Move much of the content
from guides/introduction.rst to docs.rst, which will serve as the new
introductory page. Remove guides/introduction.rst.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Scally <dan.scally@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

Documentation/conf.py

@@ -37,8 +37,11 @@ author = u'Kieran Bingham, Jacopo Mondi, Laurent Pinchart, Niklas Söderlund'
 # extensions coming with Sphinx (named 'sphinx.ext.*') or your custom
 # ones.
 extensions = [
+    'sphinx.ext.graphviz'
 ]
 
+graphviz_output_format = 'svg'
+
 # Add any paths that contain templates here, relative to this directory.
 templates_path = []