fully support paging in gui

[abma]

i.e.:

https://springfiles.springrts.com/search.py?offset=3000&metadata=1

is supported now.

[springraaar]

on #85 , the full result set is retrieved from the server (at least the limit's been increased) and the "more..." button in gui can be clicked repeatedly to progressively reveal it in chunks of 60 (the filtering is client side)