e, it is responsibility of programmer to periodically 
clean object cache to avoid memory overflow. Without cleaning cache, all objects from the database will
sooner or later be loaded in memory. If database size is larger than size of available main memory, 
it can cause application crash. But even if database fits in main memory, cleaning cache can significantly
increase performance, because adding object to hash table is very slow in Rebol and looks like it has 
quadratic complexity (adding N objects req