Improve paging by changing the filter instead of using skip, if an order is specified

[hylkevds]

Skipping rows is slow, since each skipped row still needs to be fully calculated.
When an orderby is used, paging can be implemented by changing the where (filter) instead. Rows skipped because of a filter do not need to be fully calculated and result in much faster queries.

[hylkevds]

The develop-2.0 branch now has this enhancement and it makes paging significantly faster.
Some limitations:

• Only works if there is an orderBy on the primary key in the list of oderBys. This can be added automatically with the alwaysOrderbyId setting.
• Only works for path ordering, not for ordering by function.