Make last_commit_date a time field

This way it will be possible to interactively select time ranges
in the Kibana graphs

Change-Id: Iaaf0d2f2f6047d433b032628efbf96f30e7c46c8
diff --git a/dashboard-importer/kibana-config/BB_index-pattern.json b/dashboard-importer/kibana-config/BB_index-pattern.json
index b6b361f..aa5ca6e 100644
--- a/dashboard-importer/kibana-config/BB_index-pattern.json
+++ b/dashboard-importer/kibana-config/BB_index-pattern.json
@@ -5,6 +5,7 @@
   "_score": 1,
   "_source": {
     "title": "gerrit",
+    "timeFieldName": "last_commit_date",
     "notExpandable": true,
     "fields": "[{\"name\":\"_id\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"_index\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":false},{\"name\":\"_score\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":false,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"_source\",\"type\":\"_source\",\"count\":0,\"scripted\":false,\"searchable\":false,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"_type\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":false},{\"name\":\"added_lines\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"author\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"author.keyword\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"day\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"deleted_lines\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"email\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"email.keyword\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"email_alias\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"email_alias.keyword\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"hour\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"last_commit_date\",\"type\":\"date\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"month\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"name\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"name.keyword\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"num_commits\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"num_files\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"organization\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"organization.keyword\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"project\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":false,\"readFromDocValues\":false},{\"name\":\"project.keyword\",\"type\":\"string\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"year\",\"type\":\"number\",\"count\":0,\"scripted\":false,\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":true},{\"name\":\"changes_per_commit\",\"type\":\"number\",\"count\":0,\"scripted\":true,\"script\":\"if (doc['num_commits'].value > 0) { \\n    return ((float) (doc['added_lines'].value + doc['deleted_lines'].value) / (float) doc['num_commits'].value);\\n} else {\\n    return 0;\\n}\",\"lang\":\"painless\",\"searchable\":true,\"aggregatable\":true,\"readFromDocValues\":false}]"
   }