Live Data UX improvements

Edit mode is now turned on and off with an "Edit mode" button, showing a pencil icon next to the Live Data menu (instead of the previous checkbox inside that menu). The button stays pressed while edit mode is on.

Any Live Data can also be maximized from its menu, to cover the whole window and focus on its entries. "Minimize" in the same menu, or the "Escape" key, brings it back to its normal state.