Fife game-engine ebuild that works on Funtoo

This modifies an exisiting ebuild by totycro present on the gamerlay
overlay to install for Python27 and not for Python3. Builds and runs
the provided demos.
Merge branch 'release/fife'

This commit enables the use of the Fife Game Engine on Funtoo.
Based on an ebuild posted by totycro@unknown-horizons.org,
with fixes to deal with presence of Python3 on Funtoo.