Improvements for sphinx in dev-setup

[mtnstar]

Activate Sphinx in dev-setup

currently sphinx is started as container, but search does not use sphinx since the env variable RAILS_SPHINX_PORT is not set by default. Setting RAILS_SPHINX_PORT=9312 in docker/rails.env activates it and it works.

Generate sphinx config on startup

currently sphinx is just using a static index config: https://github.com/hitobito/development/blob/master/docker/sphinx.conf

so only core attributes are searchable and extended indexes from the wagons are ignored

the goal is to generate the sphinx dynamically on start-up (docker-compose up) with thinking_sphinx gem

ToDo

• Activate sphinx search in dev setup by default if there's no veto
• Fix running of sphinx specs Ausführen von sphinx tests #15
• Use dynamically generated sphinx index conf instead of static one