Map CSV columns to EE data

[mnelson4]

After a file has been uploaded, the event manager should be able to choose which CSV columns related to what EE data.

EE data they can relate to:

• Attendee columns (first name, email, city, etc)
• registration columns (status, reg date, reg final price, paid, code, count, group size)
• transaction columns (status, total, paid)
• payment columns (source, amount, payment method, gateway response, txn_id_chq_nmr, po_number, extra_accounting)
• answers (multi-valued answers can use commas or pipes to delineate values)

Possibly on this initial MVP, depending on time:

• ticket (ID or name)

After initial release:

• event name/ID

I'm thinking we'll just store this configuration in an option.

[mnelson4]

Just pushed some code that adds this. I kinda flew through it because I expect to need to change it once I get into the details of importing the data.