Support joins from sqlite tables in tile-join (#308)

* Sketching out sqlite options for tile-join

* Enable sqlite3 serialized multithreading

* Fix some unnecessary round trips from std::string to char * and back

* Gathering join keys for sql query

* Make a query

* Actually open the gpkg. Fix the query quoting.

* Actually do the query and get results back

* Join the attributes onto the feature

* Set matched if the sql join matches

* Add a flag to get the feature ID from the query

* Observe attribute exclusion when joining from sql queries

* Add a flag to exclude all attributes from the tile side of the join

* Make tile-join bounding boxes reflect feature bounds, not tile bounds

* More tests

* An empty tileset has empty bounds at null island

* Gather the results from each thread *after* the thread finishes

* Missed a test

* Fix accidental inclusion of the top left of the tile in the bbox

* Case smashing and prefix trimming in the select

* Add test of sql join

* Make the join column option a join expression option

* Fix antimeridian adjustment. Z0 can't wait until the end of the tile

* Checkpoint on accepting multiple joined rows per tiled feature

* Adding the joined attribute should be per-feature, not per-attribute

* Forgot to update the test. Order of joined attributes has changed.

* Get the attributes back in the right order

* Add test of sql join with limit

* Allow multiple tile features to have the same join key

* Update tests for a country name with two distinct geometries

* Update version and changelog

* Forgot to mention the bounding box improvements

tests/ne_110m_ocean/join/joined.mbtiles.json

@@ -1,5 +1,5 @@
 { "type": "FeatureCollection", "properties": {
-"antimeridian_adjusted_bounds": "-180.000000,-85.051129,180.000000,85.051129",
+"antimeridian_adjusted_bounds": "0.000000,-85.051129,359.912109,85.051129",
 "bounds": "-180.000000,-85.051129,180.000000,85.051129",
 "center": "-45.000000,33.256630,4",
 "description": "tests/ne_110m_ocean/join/ocean.mbtiles",