Collection Info (i) Icon loads dataset variables and Granule Availability chart very slowly without notifiying the user of loading

[jamesfwood]

On each collection's info page (the i Icon), it loads the Dataset Variables and Granule Availability in the background. It is slow to populate, so it should at least display a "Loading..." message to notify the user that data is being populated. It also behaves very strangely when it's in the middle of loading and trying to use the Chart. Should wait until the full chart is done loading before displaying.