Story #3875: Create a dashboard (version 1) for DataONE to provide high level overall system status
Add a times series chart of uploads and downloads on the summary page
After feedback from the CCIT meeting, we are planning to remove the stacked bar chart from the Summary tab in the dashboard, in favor of a time series chart of uploads and downloads for all MNs. The bar chart compares total counts across MNs, which may not be desirable. The TimeSeriesView used in the per-MN view can be repurposed for the summary page. Start with uploads over time, and when Robert is finished with #3886, incorporate downloads. The chart should have a filled curve, using an uploads color matches the 'total files' dark teal color. The downloads curve fill color should match the 'data downloads' plum. Decide if these charts should be toggled (one at a time), or if both series can be plotted together. Scaling may be an issue for that latter.
The TimeSeriesView code was an adaptation of http://bl.ocks.org/mbostock/3885211, and so the 'browser' and 'browsers' variables are holdovers from that example, and should be changed to represent objects. Also, the TimeSeriesView uses colors from d3.scale.category20(). Change this such that we use the DataONE-specific colors.