Structure for raster samplers for a datasource
Structure for raster samplers for a datasource

- Also adds a bool member to check if this datasource will actually construct any geometry, and
if so then its tiles will be created/managed by the tile manager, else not.

quitejonny/tangram-es,cleeus/tangram-es,tangrams/tangram-es,tangrams/tangram-es,cleeus/tangram-es,tangrams/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,cleeus/tangram-es,quitejonny/tangram-es,cleeus/tangram-es,tangrams/tangram-es,quitejonny/tangram-es,tangrams/tangram-es,quitejonny/tangram-es,tangrams/tangram-es,tangrams/tangram-es