[BUG] movingMedian doesn't handle gaps

[jonasbleyl]

The movingMedian function does not fill in the gaps when applying it over data. This works correctly in graphite-web.

Here is an example with data that has several 1m gaps. When applying movingAverage(5min), movingMax(5min), etc the gaps are filled in correctly. When using movingMedian(5min) however the gaps are not all filled in and in some cases it causes the gaps to be even larger. The xFilesFactor option seems to have no effect on this either.