Improvements to error state: input outline shows with or without focus, and added new error div which shows if there's an error, but goes away if the user starts changing what they had submitted in the input. Removing a lot of code surrounding the tooltip which has now become unnecessary.

Import input now shows error state w/orange border around input and tooltip with static error message.

Initial SB2 Import UI (button in preview modal + import modal that can load projects via url). Preliminary validation on url, still needs error handling.