added pagination methods

[Robotv2]

[RedstoneFuture]

According to the documentation, negative pages are also possible at the moment:

"Note that the pages don't necessarily have to follow each other up; you can add a fifth page (index four) without having a fourth page (index three), or you can have negative pages, such as -1, -2, etc. however this is heavily discouraged."

For normal purposes, however, an "isFirstPage" and "isLastPage" method is very useful.