Allow user to specify lender reference for a loan
Show lender reference on loan detail page
Include lender reference in loan CSV export
Add lender reference to loan report
Don't copy lender's loan reference when transferring a loan

Allow lender's reference to be set during loan entry for the new loan.
Add lender reference to settle loans pages and CSV export
Add lender reference to realise loans pages and CSV export
Add searching by lender's loan reference
Merge pull request #112 from alphagov/add_lender_reference_to_loan

Add lender's internal reference to loan