This was an extra level of attribute indirection (features point
to metadata records which point to key and value strings) which was
intended to reduce the size of temporary storage for features with
large numbers of attributes that were also spread across large numbers
of tiles at maxzoom.
For other kinds of features, the extra indirection slowed things down
instead, and, especially when maxzoom guessing was being used, many more
features were having their metadata externalized than could actually
benefit from it.
* Improve maxzoom guessing for tightly-clustered point data sources
* Go back to the old distance estimate, since it is less mysterious
* Update changelog and version
* Add --maximum-zoom-at-least to specify a minimum maxzoom to guess
* Check whether the specified minimum maxzoom is out of range
* Rename the option to --smallest-maximum-zoom-guess
* Update tests, changelog, and version
* Handle points too when dropping or coalescing the "smallest" features.
* Add statistics of tile size reduction strategies to tileset metadata
* Update changelog and version
* Update documentation
* Change JSON objects to a union type to use less memory
* Stop storing the string representation of JSON numbers
* Restore the ability to create features with large integer attributes
* Make sure large-integer feature IDs still behave as before
* Add missing #include
* Don't preallocate as much space for arrays and objects
* Treat inability to check free disk space as a warning, not an error
* Update changelog and version
Erica Fischer