Fix pagination for FindAll method

[dmaksimov]

The FindAll method was returning on the wrong results when using pagination.

The $pageNumber argument was being passed directly to the query as the startPosition instead of determining what the startPosition should be based on the $pageNumber and $pageSize.

This PR determines the correct startPosition for the query.

The $pageNumber argument default has been updated to 1 since that makes more sense. When thinking about pages we think of them as starting at 1 not 0.

---

Example

Say you had 25 items and were wanting to return them all in pages of 10.

Page 0

$dataService->FindAll('Item', 0, 10);

Result:

select * from Item startPosition 0 maxResults 10
/* returns items 1-10 */

Expected:

select * from Item startPosition 1 maxResults 10
/* returns items 1-10 */

(this is redundant and the same as page 1)

Page 1

$dataService->FindAll('Item', 1, 10);

Result:

select * from Item startPosition 1 maxResults 10
/* returns items 1-10 */

Expected:

select * from Item startPosition 1 maxResults 10
/* returns items 1-10 */

Page 2

$dataService->FindAll('Item', 2, 10);

Result:

select * from Item startPosition 2 maxResults 10
/* returns items 2-11 */

Expected:

select * from Item startPosition 11 maxResults 10
/* returns items 11-20 */

Page 3

$dataService->FindAll('Item', 3, 10);

Result:

select * from Item startPosition 3 maxResults 10
/* returns items 3-12 */

Expected:

select * from Item startPosition 21 maxResults 10
/* returns items 21-25 */

[LiamAshdown]

#473 Can this be merged please?