LUCENE-5675: initial scaffolding for new IDVPF

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene5675@1594971 13f79535-47bb-0310-9956-ffa450edef68
LUCENE-5675: add docs/AndPositionsEnums

git-svn-id: https://svn.apache.org/repos/asf/lucene/dev/branches/lucene5675@1594985 13f79535-47bb-0310-9956-ffa450edef68