Add metadata to 2d maps/tiles

[tst-blaird]

Issue #1012 identified an problem and implemented a fix that works but is not optimal. The problem identified in #1012 does not affect 3d portable globes because of the metadata which gives cutter information on what higher resolution imagery it needs to gather. Similar metadata should be added to 2d portable maps so we can build a correct and complete portable map without needing to use the "Continue past empty levels" option added in #1012.