add a panel stage transition button in GUI

add a button to do panel stage transition in the GUI.

To avoid conflicts, please merge this MR first: !72 (merged)

This button contains a dropdown menu for users to select what stage you want to transit the panel to:

Once you hit the button, it will check whether the selected stage is after the current stage, and also check if all tests have passed in current stage, and will give error message if not:

Users can also check the "force" check box to skip those checks and do the transition regardless:

Details of failures can be found in terminal output: