[prometheus] Use `panelId` and `target.refId` for requestId

Using these two values ties requests to a
particular query position within a panel, ensuring
that requests are canceled if:

- Duplicate requests with the same query are sent
- Requests from the same query position (but a
different query) are sent

The last point is important as it identifies
queries by a physical location in the dashboard
instead of with the query expression.  If a
different query from the same position in a panel
is sent, the previous request should be canceled.

Update debian.md to Debian Jessie

(cloudwatch) add metrics

properly quote font-family on singlestat

Fix node version in package.json

Value was incoherent since
https://github.com/grafana/grafana/commit/1900c81d9f9507ed4dbd18e95569480dfd0922f7

Escape html chararcters in singlestat renderer

closes #4740

Issue #4740 - able to use $SeriesName variable in prefix of postfix.

fix z-index order in Series Overrides

add cloudwatch metrics

closes #4674