Cache mode storage

Starting from version 3.2.16 mnoGoSearch does not support the so called cache mode anymore. Cache mode used its own storage engine to store the words index. It was in many cases faster than the SQL-based words index, but it was very buggy and unstable, and in fact it was almost impossible to use it in a serious production environment. The decision was made to stop supporting cache mode and to concentrate on improving the SQL-based modes.

Starting from version 3.2.36 mnoGoSearch supports DBMode=blob for both indexing and search. It is a replacement for the old cache mode, which is both fast and stable.