[geo] provide more flexible Spatial controls (#4032)

Before this PR the only way to query lat/long is in the shape of 2
columns that contains lat and long.

Now we're adding 2 more options:
* a single column that has lat and long with a delimiter in between
* support for geohashes - geohashes are cool

superset/assets/javascripts/explore/components/controls/index.js

@@ -10,6 +10,7 @@ import FixedOrMetricControl from './FixedOrMetricControl';
 import HiddenControl from './HiddenControl';
 import SelectAsyncControl from './SelectAsyncControl';
 import SelectControl from './SelectControl';
+import SpatialControl from './SpatialControl';
 import TextAreaControl from './TextAreaControl';
 import TextControl from './TextControl';
 import TimeSeriesColumnControl from './TimeSeriesColumnControl';
@@ -29,6 +30,7 @@ const controlMap = {
   HiddenControl,
   SelectAsyncControl,
   SelectControl,
+  SpatialControl,
   TextAreaControl,
   TextControl,
   TimeSeriesColumnControl,