Make dataset selection independent on Data and Output tabs

[shapiromatron]

Currently the selected dataset on the Data and Output tabs are synced, that is, if a user changes the selected dataset on one tab, it persists in the other. Update so that tab changes are independent.

We'll likely keep the dataStore injection, but the input props will change so that these props which will come from the relevant store are passed in (eg; feel free to adjust):

<DatasetList
   selectedModelIndex={outputStore.selectedModelIndex}
   onChange={outputStore.handleSelectedDatasetChange} />