internal cleanups on the API used to convert map zoom levels to the parameters needed to generate quadkeys for data tiles.
this should also prevent mixed release plugins/test IITC builds causing issues with it's 'show more portals' plugin
further changes are planned - by lying to the backend about the map zoom to optimise the portal detail level (density) returned and make better use of the data cache. needs some practical experimentation to get good adjustments, and a cleaner API for these plugins
add tweaks of data retrieval zoom level, to make better use of the cache and be friendlier to the API in some cases
also, default-intel-detail and show-more-portals plugins fixed - the logic has been moved into IITC core, with the plugins just setting flags to change behaviour
website: updated for 0.16.5 release
artifacts: centralise the descriptions of the artifact types/fragment names, and fix an incorrect warning concerning the new amar artifacts
bump version number
Merge remote-tracking branch 'upstream/master'