Merge branch 'stable-2.14' into stable-2.15

* stable-2.14:
  GroupField: Change UUID fields' type to KEYWORD
  Add keyword type to index type system
  Elasticsearch: Encapsulate supported versions in an enum

Change-Id: Ic30a5bc0c69623a22f1305c96bfa70e3daeed054
tree: 8d1a92934e6ed4c1cf2076cf3dba6e5305400cf1
  1. gerrit-acceptance-tests/
  2. gerrit-elasticsearch/
  3. gerrit-pgm/