Field LUCENE_MAIN_VERSION

this is the internal Lucene version, recorded into each segment. NOTE: we track per-segment version as a with the "X.Y" format (no minor version), e.g. "4.0", "3.1", "3.0".

Alpha and Beta versions will have numbers like "X.Y.0.Z", anything else is not allowed. This is done to prevent people from using indexes created with ALPHA/BETA versions with the released version.