Improvements to power hour importing

[patricktemple]

Before I push to prod, do the following:

• Figure out if this is the right data model, separating out power hour from attachments.
• Allow adding power hours manually to the list? Or deleting?
• Allow editing attachments too?
• Allow importing from any spreadsheet not just old auto-generated power hours?
• Fix the handling of the "Notes" field on the legislator which is now confusing, the fact that it's inserted into the sheet.

[patricktemple]

Fixed the notes issue.