Finally figured out dh_sphinxdoc

Was missing package.docs (undocumented, ironically) to copy doc output
from sphinx's build area to the package build directory, and an
extension to the dh_installdocs rule to cause sphinx to actually build
the docs. Also added a package.doc-base file for registering the docs.
Can't use pybuild / dh_python

It's only available on platforms with Python 3.3 or above (Raspbian, and
Ubuntu Precise are stuck on 3.2). So, back to distutils ... Also fixed
up some incorrect target filenames
Fixed color_effects doc reference

Many thanks to jbeale for the bug report!
Remove pybuild stuff from rules

pybuild's not available on debian, so it's back to python_distutils
buildsystem ... which doesn't seem to work
Fix up install location

The dh_auto_install rule was placing its output in the wrong place for
some reason (and also wasn't generating a separate Python 3-based
install). This override fixes the issue, so that the pi can now produce
valid python 2 and 3 binary deb packages
Fix option block errors when generating docs

When generating docs for the python-picamera-docs package on the pi,
sphinx complained about invalid option blocks for a couple of note
admonition sections. Apparently there should be a blank line (not
mentioend in the docutils docs?) before the first line of content for
these blocks.