* initial raster support
* _st_intersects_geom -> _st_intersects_geom_nband
* add tests
* update docs
* improve docs
As requested by @marionschleifer
* new type for raster values
Suggested by @lexi-lambda
* replace `SEUnsafe "NULL"` with SENull
Changes compared to `/v1alpha1/graphql`
* Changed all graphql responses in **/v1/graphql** endpoint to be 200. All graphql clients expect responses to be HTTP 200. Non-200 responses are considered transport layer errors.
* Errors in http and websocket layer are now consistent and have similar structure.
