[Ingest] Add De-dot Processor

[talevy]

Since fields with dots in the name are disallowed from being indexed, it is useful to have an ingest processor that can help replace those .s into some other character (e.g. _).

[talevy]

@martijnvg @javanna
I started the work for this here: https://github.com/elastic/elasticsearch/compare/feature/ingest...talevy:ingest-dedot-processor?expand=1
but I have a few questions about its functionality.

should this recursively search and replace across all fields? should we supply a list of fields?

I left it to only search and replace across top-level fields. I also noticed some behavior that I thought was unexpected within the mustache templating against documents with dots in them. I added two tests to demonstrate the existing behavior.

[javanna]

I left a couple of comments on your commit. I think we should look for fields that contain dots recursively. I had a look at the mustache tests and left comments about those too.

[eskibars]

+1 to doing this recursively

[talevy]

processor merged into feature/ingest branch. closing.

[animageofmine]

@talevy
What happened to dedot processor? Was this removed or replaced with something else?