Revert "Fix celery: we can't pickle modules (bug 1013874)"

This reverts commit 416c78e3b04f51d4286757d36973449b98e44b1c.
Revert "optimize ES reindexing by using bulk (bug 1013874)"

This reverts commit 9242daba450615702cd10e28387f1761d4c56016.
Revert "Change ES config on build.sh (bug 1013874)"

This reverts commit 60793e9e5f142adad4d3b82becac9296bee292d6.
Revert "Bump Elasticsearch version (bug 1013874)"

This reverts commit fd979d80e54a28e2b1a1c8f15e7674c879ee4bf0.
Revert "Upgrading Elasticsearch (bug 1013874)"

This reverts commit a403c604f728879476b61b103a0fd7d01b39bf4b.