============
The default unit for measuring distances is *MILES* in most cases. This commit moves ES
over to the *International System of Units* and make it work on a default which relates
to *METERS* . Also the current structures of the `GeoBoundingBox Filter` changed in
order to define the *Bounding* by setting abitrary corners.

Distances
---------
Since the default unit for measuring distances has changed to a default unit
`DistanceUnit.DEFAULT` relating to *meters*, the **REST API** has changed at the
following places:

  * `ScriptDocValues.factorDistance()` returns *meters* instead of *miles*
  * `ScriptDocValues.factorDistanceWithDefault()` returns *meters* instead of *miles*
  * `ScriptDocValues.arcDistance()` returns *meters* instead of *miles*
        one might use `ScriptDocValues.arcDistanceInMiles()`
  * `ScriptDocValues.arcDistanceWithDefault()` returns *meters* instead of *miles*
  * `ScriptDocValues.distance()` returns *meters* instead of *miles*
        one might use `ScriptDocValues.distanceInMiles()`
  * `ScriptDocValues.distanceWithDefault()` returns *meters* instead of *miles*
        one might use `ScriptDocValues.distanceInMilesWithDefault()`
  * `GeoDistanceFilter` default unit changes from *kilometers* to *meters*
  * `GeoDistanceRangeFilter` default unit changes from *miles* to *meters*
  * `GeoDistanceFacet` default unit changes from *miles* to *meters*

Geo Bounding Box Filter
-----------------------
The naming of the GeoBoundingBoxFilter properties allows to set arbitrary corners
(see elastic#4084) namely `top_right`, `top_left`, `bottom_right` and `bottom_left`. This
change also includes the fields `topRight` and `bottomLeft` Also it is be possible to
set the single values by using just `top`, `bottom`, `left` and `right` parameters.

Closes elastic#4515, elastic#4084