Fixing issues in key-value database

[rickb80]

Issues fixed:

1. Managing misses in the KV database: Using ReadTree when the version to be readed could have been evacuated from the KV database.
2. Adding zeros into the cache to avoid accesses to the database.
3. Fixing the functionality of multi-write for the key-value table, the search must consider intervals.
4. Ensuring that the DatabaseKVAssociativeCache is shyncronized with the kv database for the newest versions