fix 'show portal weakness, so it sets the fill, rather than border, colour when marking a not-weak portal
render limits are obsolete with the new code - remove contents of plugin
(file remains so users auto-updating get this 'empty' version)
show-more-portals plugin updated to work better with new map tiles
more work on map data rendering rewrite
marker creation/style changing moved out of rendering code (to allow use from elsewhere, and possible overriding by plugins)