Rewrite import_dashboards.sh script in go (#2155)

* Generate Kibana index pattern from etc/kibana/fields.yml

The format of each field can be specified in fields.yml using the `format` option.

Generate Kibana index pattern for all the elastic beats by running `make update`

* Re-write the import script in golang, to have one script for windows and unix systems instead of two scripts (bash
+powershell).

The script imports the dashboards together with visualizations, searches and index pattern for a Beat in Elasticsearch.
The script is added to the Beat package.

* fix makefile

* address comments

CHANGELOG.asciidoc

@@ -70,6 +70,7 @@ https://github.com/elastic/beats/compare/v5.0.0-alpha5...master[Check the HEAD d
 - Add kafka message timestamp if at least version 0.10 is configured. {pull}2190[2190]
 - Enhance contains condition to work on fields that are arrays of strings. {issue}2237[2237]
 - Lookup the configuration file relative to the `-path.config` CLI flag. {pull}2245[2245]
+- Re-write import_dashboards.sh in Golang. {pull}2155[2155]
 
 *Metricbeat*
 

Makefile

@@ -1,3 +1,4 @@
+
 BUILD_DIR=build
 COVERAGE_DIR=${BUILD_DIR}/coverage
 BEATS=packetbeat filebeat winlogbeat metricbeat
@@ -64,8 +65,8 @@ simplify:
 # Collects all dashboards and generates dashboard folder for https://github.com/elastic/beats-dashboards/tree/master/dashboards
 .PHONY: beats-dashboards
 beats-dashboards:
-	mkdir -p build
-	$(foreach var,$(PROJECTS),cp -r $(var)/etc/kibana/ build/dashboards  || exit 1;)
+	mkdir -p build/dashboards
+	$(foreach var,$(BEATS),cp -r $(var)/etc/kibana/ build/dashboards/$(var)  || exit 1;)
 
 # Builds the documents for each beat
 .PHONY: docs

libbeat/.gitignore

@@ -8,6 +8,7 @@ _output
 /docs/html_docs
 .vagrant
 build
+/dashboards/import_dashboards
 
 # Architecture specific extensions/prefixes
 *.[568vq]