Add a way to specify no-tracking to reduce caching on demand

[MikeAlhayek]

Fix #523 Fix #522

[hishamco]

Can we add it as an extension method AsNoTracking or WithNoTracking instead of passing a context in each method

[MikeAlhayek]

@hishamco I thought about it originally. The problem if we do that, we would have to track the state whether to track the entities per session not per query. The idea is to be able to not track the results per-query not per-session. Like what if the users wants to first query non-trackable documents, and in the same scope, they want to query other trackable documents? If they don't remember to set the state before the second query, both queries will not be tracked.

I simplified things by adding WithNoTracking() method of the IQuery<T> so if you are building a query, you can use this method to pass instruction to not track the entries.

But, in the Session, I think it is better to provide QueryContext that would change the behavior of the query on demand.

[MikeAlhayek]

Now looks much better for me, waiting for Seb comment

@hishamco If you spent time to review a PR, you may want to consider approving what you think is ready. This way, any changes you request will be to eventually to approve the PR which is more helpful than just leaving comment :)

[hishamco]

Just fixing a small comment then I will approve

LGTM

[sebastienros]

Internal caching can be very expensive when dealing with a large data set.

I don't think it adds much more overhead since it's only adding the items to a collection, and "dealing with a large dataset" means you will also do that. You should just get rid of the session when you are done with it and you don't want to keep the references around.

However I can see why you would not want to have to create a new Session for every page of data you load, by convenience, and you came up with the notion of QueryContext. I think it should still be in the Session and not at the query level. This way you create a session that doesn't save the state and can reuse it to do all your queries. So I would suggest to just add a property to the session to disable tracking altogether. And another advantage is that the object won't even be added to the identity map at all, so potentially even faster processing. This would be an optional bool in CreateSession. I don't think it matter to be able to change the state of the session to enable/disable tracking dynamically. Just create a new session if you need different characteristics.

Also can you rename DetachRange to Detach(IEnumerable<object>) instead? Unless you have an argument that makes it better.

[MikeAlhayek]

@sebastienros I made the requested changes.