Gaia Platform 0.3.1-beta

What's Changed

• Fix direct_access/README.md not exported with SDK by @simone-gaia in #1010
• Don't allow dropping tables that still contain data by @chuan in #1011
• Switch gaiac direct access message output from cerr to cout by @chuan in #1013
• cleanup rocksdb txn objects post commit/rollback by @mihirj1993 in #1014
• Don't clear metadata before transitioning chunk to owned state by @senderista in #1015
• Add a readme for the SDK by @vDonGlover in #1008
• Bump Gaia version to 0.3.1-beta by @simone-gaia in #1016

Full Changelog: v0.3.0-beta...v0.3.1-beta