Log message:
Add p5-Data-Page-Pageset 1.02

Pages number can be very high, and it is not comfortable to show user from
the first page to the last page list. Sometimes we need split the page list
into some sets to shorten the page list, the form is like:

 1-6 7-12 13 14 15 16 17 18 19-24 25-30 31-36 37-41

the first two part indicats the two pagesets, and in current pageset, we
provide the normal page list from the first one to the last one, and provide
the rest pagesets to indicate the pages scope.

In this module, you can specify the pages_per_set or max_pagesets for fine
showing.