Text search solver: easier ElasticSearch startup

[aimichal]

The text search solver setup instructions require manually populating an Elastic Search index:

https://github.com/allenai/aristo-mini/blob/master/solvers/textsearch/src/main/scala/org/allenai/aristomini/solver/textsearch/README.md

This could be simplified:

• Pre-process a corpus and distribute bulk commands directly
• Pre-populate the search corpus and distribute the data/ directory contents

[aimichal]

Script bin/insert-text-to-elasticsearch.py was created to simplify inserting text into an Elasticsearch index. See pull request https://github.com/allenai/aristo-mini/pull/18.