Allow for plugin testing.

Bring panel alert to front and move tooltip to top.

This makes the panel a lot easier to mouse over without odd visual effects.

With this change in place you can include plugin specs in `grunt test` by creating a `src/config.js` like that includes something like this:

```js
      plugins: {
        // list of plugin panels
        panels: [],
        // requirejs modules in plugins folder that should be loaded
        // for example custom datasources
        dependencies: ['grafana-plugins/atlasDatasource'],
        specs: ['grafana-plugins/specs/atlasDatasource-specs']
      }
```

Graph: Fix for y axis and scaled units (GiB etc) caused rounding, for example 400 GiB instead of 378 GiB, Fixes #1251

Panel: duplicate now always adds the duplicated panel on the same row instead of creating a new row, Closes #1185

Graphite: alt node suggestions will now not include wildcard or template variables if the node is empty, Closes #1230

fix #1204: add separate datasource parameter withCredentials

Add offsetToZero to gfunc.

allow multiple params for sumSeriesWithWildcards

Graphite: movingAverage / movingMedian parameter type impovement, now handles int and interval parameter, Fixes #1207

Singlestat: small fix for threshold evalutations, use greater or equal for threshold checks, Fixes #1192

Extend tooltip for drilldown link

Added graphite function 'useSeriesAbove'

It took me a bit to find out that variables need to be passed with var-variableName. 
The behavior is not specific to the drilldown link but I couldn't find it in any documentation elsewhere and it might help others to have it documented right here.