show releases on activity report charts

[rlskoeser]

• use d3-annotation and tag data from releases data file
• ignore micro releases or the graph will be too crowded
• highlight annotations by project when a single project is selected in the legend (maybe hide by default?)
• update annotations when the graph zooms in and out (brush handling)
• maybe separate out releases for major projects and supporting repos — show releases for major projects on the top graph and releases for supporting repos on the bottom, since they typically don't have story points anyway

Activity report template could also include a list of major releases, analogous to what is included on iteration reports and single project reports.