[BZ 980765] Groups with more than 20 resources don't display in Multi-line composite graph.
 The d3 color palette gives us 20 shades of colors; this along with the fact that waiting for more than n +1 queries to execute (even though they are in parallel - the browser is still a single thread) makes graphing groups of larger than 20 resources prohibitive. This fix places a maximum bounds of 20 resources for the multi-line graph.