Ability to set default geo_point value

[kurtado]

Spoke with @nknize about the possibility of setting a default geo_point lat/lon value, and he said it would be possible to add this feature.

[rjernst]

What do you mean by default? null_value like we have for other field types?

[ideadapt]

null_value is still not supported for geo_point fields. But its possible to use a set processor as requested and implemented with #17659 (using "override": false option). Processors transform a document to be indexed, before it is given to the indexer.

@kurtado Does this new ability work for you?