feat(influxdb): enhancements and bug fixes

[ichiong]

Summary of changes:

• adding indluxdb docs to guide users on how to use this plugin: metric-set-query-config.md
• changes to InfluxDbResponseConverter.java is to fix kayenta-influxdb plugin when it returns or throws an error if the result that we got from influx contains values that are of type float or double.
  • example error that we get: class java.lang.Double cannot be cast to class java.lang.Integer (java.lang.Double and java.lang.Integer are in module java.base of loader 'bootstrap'.
  • The InfluxDbResponseConverterTest.java contains unit tests for these changes.
• changes to InfluxDbMetricsService.java is to fix situations when an influx query returns no results:

• changes to InfluxDbQueryBuilder.java and InfluxdbCanaryMetricSetQueryConfig.java are to add customInlineTemplate just like in other kayenta plugins such as Prometheus and New Relic to support more advance IQL statements (e.g. queries with custom tags and group by clauses)
  • InfluxdbQueryBuilderTest.java contains unit tests to test these changes

[spinnakerbot]

The following commits need their title changed:

• 3cf91dee407c7169919217f13151c4e7fbd69299: adding docs

• f41c7f421d344b4652762caebbb283b3db79b016: update influxdb docs

• fb0f1fbd85249d09fc776d65dce76ecae2a6af76: spacing

Please format your commit title into the form:

<type>(<scope>): <subject>, e.g. fix(kubernetes): address NPE in status check

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[fieldju]

Brings tears to my eyes seeing that UI and Logo!