Add support of "pagination" of tracker results

[antonsoroko]

Just an theoretical idea: it would be nice to have support of "pagination" (when tracker show several pages with results).
It is quite optional feature since usually we use search URLs with sort by seeds and usually number of results on the first page is larger than burst setting about "maximum results from provider".
But i guess for some trackers (the ones that show small number of results per page) this feature could be useful.

[elgatito]

@antonsoroko Usually we have limits per-provider to avoid bombing websites requesting Torrent files or subpages.

To implement paging we need to have another html selector for pages and implement a loop through pages somehow, knowing where we visited.