Add convert_date_string helper
[bug 857416] Fix infinite redirect problem

This sets DEV_LANGUAGES in local.py-dist because there are cases where
it doesn't get set in funfactory.

This also slims down locale.py-dist, updates the documentation, and
clarifies how things are set up.
Default ES_LIVE_INDEXING on local installs to False

The hacking howto considers ElasticSearch advanced setup, so the
local.py-dist should be start with ES_LIVE_INDEXING set to False.
Update elasticsearch docs regarding the version to use