X.PagedList: PagedListExtensions: Fix logic in ToPagedList()

[adschmu]

The command flow in ToPagedList with totalSetCount appears odd:

• For totalCount <= 0, we should simply return an empty list

• For supersetCount <= pageSize, we should not need additional conditions to simply read the list

• From totalSetCount.HasValue, we know whether to use Count(), but not whether or not to use Skip/Take

• Count() is always executed, even if we supply totalSetCount, which will create useless iterations and/or DB roundtrips if we already know the size.

As a consequence, it appears more appropriate to use the logic from X.PagedList.EF here as well (only in the sync version), which addresses all the mentioned issues.

Fixes: #266

[adschmu]

Found a broken test with this change and added the fix here as well.