Push by default to gerrit/analytics index

All the Kibana dashboards and index template configuration are
related to gerrit/analytics index. Use it as default to allow an
easier use of the default settings of the ETL invocations.

Change-Id: I4c1e8ddad465a225cf9a00266d7c19512f68688b

src/main/scala/com/gerritforge/analytics/plugin/StartCommand.scala

diff --git a/src/main/scala/com/gerritforge/analytics/plugin/StartCommand.scala b/src/main/scala/com/gerritforge/analytics/plugin/StartCommand.scala
index f09fe2d..b2d9da5 100644
--- a/src/main/scala/com/gerritforge/analytics/plugin/StartCommand.scala
+++ b/src/main/scala/com/gerritforge/analytics/plugin/StartCommand.scala
@@ -26,7 +26,7 @@
 
   @ArgOption(name = "--elasticIndex", aliases = Array("-e"),
     usage = "index name")
-  var elasticIndex: String = null
+  var elasticIndex: String = "gerrit/analytics"
 
   @ArgOption(name = "--since", aliases = Array("-s"), usage = "begin date")
   var beginDate: Timestamp = NO_TIMESTAMP