(cloudwatch) fix template variable expanding

Fix typo in PLUGIN_DEV.md

After switch from systemjs to webpack, needed to import the
file-saver saveAs shim for it work. Fixes #9525

closes #9539

Also, fix for coremodules export. Have to add the __esModule
attribute to fool SystemJS.

CloudWatch: Add ALB RequestCountPerTarget metric

fix cloudwatch query error over 24h

(cloudwatch) show error message when cloudwatch datasource can't add

This commit adds the new ALB metric `RequestCountPerTarget` which was
released in July 2017.

Missing dot in aws credentials path

As far as i know the path hasn't changed, but the dot is missing in one place.

makes it possible to have a second condition requering
at least X points of data.

Update rpm.md

for error "The GPG keys listed for the "grafana" repository are already installed but they are not correct for this package."

ref #9476