* Fix bug: too many cloudwatch metrics
Cloudwatch metrics were being added incorrectly. The most obvious
symptom of this was that too many metrics were being added. A simple
check against the name of the metric proved to be a sufficient fix. In
order to test the fix, a metric selection function was factored out.
* Go fmt cloudwatch
* Cloudwatch isSelected checks metric name
* Move cloudwatch line in changelog to 1.2 features
* Use shared AWS credential configuration.
* Cloudwatch dimension wilcards
* Allow configuring cache_ttl for cloudwatch metrics.
* Allow for wildcard in dimension values to select all available metrics.
* Use internal.Duration for CacheTTL and go fmt
* Refactor to not use embedded structs for config.
* Update AWS plugin READMEs with credentials details, update Changelog.
* Fix changelog after rebasing to master and 0.13.1 release.
* Fix changelog after rebase.