AbiathRPC - Tileinfo download

Yesterday I added full tileinfo support to AbiathRPC, minus support for it in the Download Levels feature. Today I filled in that gap. Since downloading the project might now get more than just levels, the menu has been renamed to simply Download. If and only if the current server has tileinfo, the export window has an extra field for the tileinfo file's name. As expected, that file is now saved right beside the levels.