[Watcher] Use index.auto_expand_replicas: 0-1 (elastic/x-pack-elasticsearch#3284)

This changes the default behavior of .watch* indices to be green on one-node clusters, instead of constantly yellow.

Original commit: elastic/x-pack-elasticsearch@cdaee7cd72

plugin/src/main/resources/watch-history.json

@@ -4,6 +4,8 @@
   "settings": {
     "xpack.watcher.template.version": "${xpack.watcher.template.version}",
     "index.number_of_shards": 1,
+    "index.number_of_replicas": 0,
+    "index.auto_expand_replicas": "0-1",
     "index.format": 6
   },
   "mappings": {

plugin/src/main/resources/watches.json

@@ -3,6 +3,8 @@
   "order": 2147483647,
   "settings": {
     "index.number_of_shards": 1,
+    "index.number_of_replicas": 0,
+    "index.auto_expand_replicas": "0-1",
     "index.format": 6,
     "index.priority": 800
   },