Ongoing thread of UI issues

[shreyashankar]

• “Dataset” column should open automatically when I click “data.json” on the left
• Also, available keys in the dataset view should populate as soon as the first document is read.
• there wasn’t an indicator that the “Dataset.json” upload was ongoing — it worked, but I thought it was a no-op because it took 10 secs or so
• available keys should not be clickable
• highlight the menu button in the operation card / make it more prominent
• the selectivity for the first operation (when there is a sample) should be special cased
• run button is hidden when dataset viewer is open
• plus button below the last operation to add a new operation
• hide the bookmarks panel so it's not so required to use it

Other DSL issues

• - reduce key should not be allowed to be empty. OR empty means all documents in a group.