adding support for Y-axis change to support avg-bw
total disk space is replaced with total avg bw (read bw + write bw)
storage node avg_bw will be cumulative sum of all the disk read and write bw.
updated storage nodes, storage node details, and disks scatter charts.
updated tooltips and new tooltip template to accomodate the wider label value pair for disks and storage node.
removed pools bar chart legend since its overlapping when there is more pools configured other than the default volume and image pool.
currently hovering over the usage shows the details about name and space used in GB
changed color scale to use the d3 category10 pallette.
Merge pull request #129 from skizhak/R1.10

adding support for Y-axis change to support avg-bw