Fix failing calls to oti service
Fetch OTI base-URL and data-repo-URL from config.
Rename oti_study_repo_url => opentree_docstore_url
Merge pull request #76 from OpenTreeOfLife/nudge-oti-index

Fixes for oti nudge, added OPENTREE_DOCSTORE_URL on config file

N.B. This will need changes once we're working in a multi-rep docstore...