Add popup with link for remarkable event star in time series

[KatiRG]

[PBrockmann]

http://highcharts.uservoice.com/forums/55896-highcharts-javascript-api/suggestions/1126429-allow-clickable-tooltips

not sure it is feasible with actual release. We should vote...

[KatiRG]

Maybe we can define milestones to define the order in which to achieve tasks.