make query_objects faster

[jeanetteclark]

I had the idea on a call that there is a way we can make query_objects much faster by keeping parts of the cache that are still relevant. Below are some changes that would need to be made

• add dateModified to the fields returned by the query function
• if a cache is found, filter to keep all objects with a dateModified older than the datetime at runtime
• query for objects only with a dateModified more recent than the datetime at runtime
• save the cache
• if no cache is found, then make sure the datetime you are querying against is very far in the past so that you get all of the objects
• remove the cache_tolerance parameter