Bucket Web UI needs controls for invoking the docloader with sample databases shipped in the server package

Once the docloader is added to the packages as part of MB-4315, the Admin Web UI needs to add controls to allow a user to load sample databases and views without needing to go to a command line.

A rough description of this interaction, to be further specified by product management, is...

The admin logs in to the Web UI, clicks on "Data Buckets" then clicks "Deploy Sample Data Bucket(s)" next to the "Create New Data Bucket" button. The Web UI then displays a message: "The sample data bucket will be approximately 100MBytes in size, on your cluster. It will be populated with sample data and sample views." with a 'continue' and 'cancel' button. The admin clicks 'continue'.

After a few seconds, there is a new data bucket in the Web UI named "sample(?)". There are sample views for this data bucket also loaded.