Invoice and line item fixes

New invoices now have only 'add line item' visible when creating. This action automatically saves the new inspection. When editing inspections, both the 'add line item' link and 'save invoice' button are visible. There is still some possibility for user confusion, but this should be eliminated when AJAX is implemented.
Inspection contact UI

Report ordered by will now show in the right column when there is an associated contact. TODO: Update remaining contact fields (property owner/report sent to) with similar UI. Correct display of information when no contact_id exists for inspection.