Consider allowing a full round trip to RequestHandler when setting a vis.uiState value

[thomasneirynck]

Using the vis-object to set a uiState value, no full round trip to the requestHandler is triggered.

Consider giving clients an opportunity to trigger a round trip to the requestHandler. This could be useful when you have want to have session-specific configs that you do not want to persist with the visualization itself. An example of this could be the sort-order of a table-column for a paginated table-component.

The vis.updateState method is not a good fit for this use-case. It only triggers a data round-trip when the vis.params change. For example, the maps can force-trigger a refresh like this when the zoom level changes, but only because the associated precision for the agg_configs changes as well.

Another option would be to give users the means to manually force-refresh. For example. by calling something like vis.forceRefresh().

[thomasneirynck]

cc @simianhacker @ppisljar