various tweaks to how IITC requests data tiles from the servers
- change TILES_PER_REQUEST to 25, instead of 10 - to match current stock intel site
- modify the zoom level faking IITC does. it still makes good use of IITC's caching, but no longer switches to a zoom level with larger tiles. recent changes to tile parameters for L8 portals on the standard intel site suggests that it's nicer to the servers to request more, but smaller, tiles, than fewer but larger ones
- restored the 'show less portals when zoomed out' plugin. however, this works differently now. rather than faking the zoom level for larger tiles, it now effectively applies the portal level filter used by the standard site. just as many requests as stock, but much smaller responses with fewer portals, so faster rendering