adding support for expansion of templated multi-select metrics

[davejhilton]

There are probably better ways to accomplish this. But this works.

The problem this solves is that with this plugin, templated values for metrics don't work when multi-select or "all" option is specified.

For example, if I create a template var $metrics = metrics(kairosdb.jvm), and click the box for "Multi Value" or "Allow All Option", then the metrics aren't resolved. It tries to run a query with a metric like this:

{kairosdb.jvm.free_memory,kairosdb.jvm.max_memory,kairosdb.total_memory}

which obviously doesn't work.

This patch expands that template-replaced grafana metric into multiple kairosdb metrics in the query, so that each can be calculated and then graphed

[davejhilton]

Closing, since #18 has been adapted to cover this case (and far better than this hack 😱 )