Multi-version allows to have one documentation version per branch.

For yukawa, this will allow us to have different documentation for
yukawa-android-14 and yukawa-android-15.

While at it, also update the title and the copyright dates in conf.py

Co-developed-by: Esteban Blanc <eblanc@baylibre.com>
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>