doc: update conf.py to match the newer template
doc: update conf.py to match the newer template

'sphinx-quickstart' now generates different output, mostly removing
commented options and instead pointing to where these are documented.
This is almost purely about looks and functionality is not changed in
any meaningful way.

Some notable changes are:

* Unicode string prefixes are removed. These are not needed. Not only
  there were no non-ASCII characters in these strings, this is
  essentially obsolete for Python 3.

* Required Sphinx version is commented out by default and there's no
  reason for this conf.py to require any particular version so, we
  leave it at the default for now. This obviously has no bearing on
  the version required by hawkmoth itself.

* Pygments style changed from sphinx to None. Mainly impacts color
  scheme.

[Jani: Keep project name capitalized. Note Pygments change in commit
message.]

jnikula/hawkmoth,jnikula/hawkmoth