* 1. after user make sql query and visualize, allow user click title to update slice title, and create a new slice at the same time.
2. don't save new title if it is empty. Will still show old title.
* change saveSlice call response and update explore view
* split reducer logic for ExploreViewContainer
* fix saveModal component and unit tests
* revert changes in SaveModal_spec.
will make another commit just to improve test coverage for SaveModal component.
* remove comment-out code
* fix merge confilicts
* [explore] DatasourceControl to pick datasource in modal
Makes it easier to change datasource, also makes it such that the list
of all datasources doesn't need to be loaded upfront.
* Adding more metadata
