Support for deep paging for Facets

[nzdev]

Support for deep paging for faceted search.

Builds on #320 and #311

Deep paging documentation applies for both Faceted and non faceted search.
Added tests.

Deep Paging

When using Lucene.NET as the Examine provider it is possible to more efficiently perform deep paging.
Steps:

1. Build and execute your query as normal.
2. Cast the ISearchResults from IQueryExecutor.Execute to ILuceneSearchResults
3. Store ILuceneSearchResults.SearchAfter (SearchAfterOptions) for the next page.
4. Create the same query as the previous request.
5. When calling IQueryExecutor.Execute. Pass in new LuceneQueryOptions(skip,take, SearchAfterOptions); Skip will be ignored, the next take documents will be retrieved after the SearchAfterOptions document.
6. Repeat Steps 2-5 for each page.

[nikcio]

@nzdev #311 has been merged to release/4.0 so could you change the target branch for this PR to release/4.0 and could you rebase or merge the branch into your PR branch to handle any merge conflicts? 😄

[nzdev]

Done

[Shazwazza]

This looks like a subset of the other PR right? #323

[nzdev]

Yes, Can be merged independently for the SortedDocValues approach.