Enable pagination result with QueryResult<T>

[marinasundstrom]

This adds the ability to get the current Total and TotalPage in the result of a query, by adding the QueryResult<T> class.

I chose to go the easy way, similar to other places in the code, parse the headers of the last request, and put them and the resulting items into QueryResult<T>.

The QueryResult is a custom collection class that substitutes the use of IEnumerable<T> as return type for IQueryOperation<TClass, QClass>.Query(...). It implements IEnumerable<T> so enumeration will still be possible.

XML documentation TBA

I will remove the Test project

[ThomasPe]

Hey @marinasundstrom, so sorry for not looking at this any sooner! Are you still interested in getting this merged?
@navjot50 any thoughts on this implementation?

[navjot50]

Hi @ThomasPe I briefly worked on the post count feature and I have some draft code here https://github.com/navjot50/WordPressPCL/tree/feature-posts-count. Basically, here I didn't introduce a custom result but rather introduced a new interface ICountOperation with a GetCountAsync where the implementation sends a HEAD request which just returns response headers without any payload (lightweight request) and then it returns the value of X-WP-Total header. This will be the minimum solution.

However, since we can introduce breaking changes in release2.0 we can go also go with a more custom result depending on what the library users want the most.