Qcables can be destroyed

- No interface yet
Refactor handling of user errors to use exceptions
Rename _find_idt to _find_lot
Move destroy onto asset, and use asset barcode

- The user doesn't have the qcable uuid when they
make the decision to destroy it. Instead they have
have the corresponding asset, and its barcode. Thus
it makes sense to move the destroy action onto the
asset controller. We still don't have the uuid.
Move behaviour from controllers into models
Update to Ruby 2.1.1
Destroy should send the correct parameters
Find lot by lot number
Add name to form elements
Error messages should use danger for formatting