Do not update charts that are out of view

[domoritz]

In large dashboards, some charts may be outside the current view and therefore don't need to be updated. It would be interesting to explore ways to not update charts that are invisible at the moment but update them when they come into view.

[willium]

• it could be interesting to explore if cube indexes could be created as charts come into view, rather than on-the-fly with selections.