Cleanup of lingering 'OTOL' references.

This involves the following substitutions across multiple repos:
    mini-otol-logo.png  ==>  mini-opentree-logo.png
    otol_api_domain     ==>  opentree_api_domain
    otol_api            ==>  opentree_api
    OTOL API            ==>  Open Tree API
    OTOL_API_BASE_URL   ==>  OPENTREE_API_BASE_URL
Merge pull request #218 from OpenTreeOfLife/otol-cleanup

Cleanup of lingering 'OTOL' references.