Multiple Cycle Upload Help Text

[anchapin]

• [ ] Update the notes at the top of mapping page to let people know that you have to map the SEED canonical column "year_ending" to one of the columns in the spreadsheet
• [ ] Add warning to mapping page if "year_ending" isn't assigned, similar to when there's not a matching column assigned
• [ ] Add text to explain what multiple cycles means in data import modal (maybe a hover over tool tip?)