Signed-off-by: wgliang <liangcszzu@163.com>

* (prometheus) cache metric suggest query result

* add test

* Prometheus: Fix actual step computation logic when a min_step is specified and the range is longer than min_step * 11000.

* Have the 'Hide series with only zeros' option also apply to series with some null values.

Fixing type of parameters from "select" to "boolean" for working with carbonapi (like it was done in summarize function) + some commas prettify.

Make it clearer that it only works with basic auth

Add the missing step of "grunt build" to the README.md

- use charset would issue additional 'SET NAMES <VALUE>' queries, set
collation would be better. see: https://github.com/go-sql-driver/mysql#charset

plugin change: make interval, cache timeout & max data points options in plugin.json, remove query.options component feature, add help markdown feature and toggle for data sources

The generated queries when selecting multiple tags are incorrect. In
InfluxQL, `AND` has a higher precedence than `OR` so the condition:

    WHERE "hostname" = 'server1' OR "hostname" = 'server2' AND time > now() - 5m

This is parsed as if it were:

    WHERE "hostname" = 'server1' OR ("hostname" = 'server2' AND time > now() - 5m)

But the intention is to write a query like this:

    WHERE ("hostname" = 'server1' OR "hostname" = 'server2') AND time > now() - 5m

This change modifies the generated query so it surrounds a query with
multiple conditions in parenthesis so it doesn't conflict with the time
expression in an unexpected way.

This is currently not an issue because InfluxDB doesn't actually
evaluate the condition for the time expression correctly. It just looks
through the AST for anything that looks like a time expression and then
assumes the proper format of `AND` was used rather than validating that
it was used correctly.

ref #9002