Adding continuation token support for LINQ

[simplynaveen20]

Continuation token will work in both the execution flow

1. Asynchronous execution via FeedIterator with extension method ToFeedIterator().

IOrderedQueryable<T> linqQueryable = this.Container.GetItemLinqQueryable<T>(
    continuationToken: continuationToken,
    requestOptions: queryRequestOptions);
IQueryable<T> queriable = linqQueryable.Where(item => (item.intField < 100));
FeedIterator<T> feedIterator = queriable.ToFeedIterator();

2. Synchronous blocking LINQ execution.

IOrderedQueryable<T> linqQueryable = this.Container.GetItemLinqQueryable<T>(
    allowSynchronousQueryExecution: true,
    continuationToken: continuationToken,
    requestOptions: queryRequestOptions);
List<T> list = linqQueryable.Where(item => (item.intField < 100)).ToList();

Closing issues

closes #537

[kirankumarkolli]