Update string field mappings to text/keyword

[Bargs]

Fixes #6409

This is a WIP to update all of the string field mappings in Kibana to either text or keyword, whichever is most appropriate for each field. In cases where I have some doubt about whether text or keyword is most appropriate I'm leaning towards text since it's matches the basic string definition we were previously using.

I've got things fixed up to a point where I can start up and use Kibana without getting any errors. Now I'm working on updating the functional tests and functional test fixtures, but I'm currently blocked by this bug: elastic/elasticsearch#16945

[rashidkpc]

Note these mapping changes are going to break for anyone upgrading from an existing Kibana 4.x installation in which they have not saved at least one of each type of saved object. Eg, if they've saved visualizations and dashboards but never saved a search, saving a search will fail.

[Bargs]

Tests are passing, so this is available if it's decided that we should move everything from string to text/keyword.

[epixa]

Marking this as blocked until we sort out the gameplan here.

[rashidkpc]

For now Elasticsearch has put support for string back into master, so at least our tests will pass again: elastic/elasticsearch@0322d49

[epixa]

How should we proceed with this PR, then?

[rashidkpc]

We need to hold on this PR until we get the reindex stuff in

[Bargs]

This can't go in until we build in a capability to reindex and version the kibana index, so I'm going to close it for now. We can continue to track the issue here #6404

[epixa]

I don't think we should conflate the two. #6404 is a blocker for this, but it should be done without also introducing all the string/keyword changes.

[epixa]

Whoops, I meant to do this to the corresponding issue, my bad.