Bug 13098: Tests for all _FixAccountForLostAndReturned use cases

Bug 13098: Tests for all _FixAccountForLostAndReturned use cases

This patch introduces tests for all the use cases for
_FixAccountForLostAndReturned. This includes the following scenarios
before _FixAccountForLostAndReturned is called:

- Full write off (the original issue)
- Full payment
- No payment or write off
- Partial payment and partial write off

Written off debts (L lines) are just skipped, any kind of payment is
added and then refund as a single credit (CR). Amount outstanding is set
to 0. Offsets need to be generated for paper trail of this decisions.

To test:
- Run:
  $ kshell
 k$ prove t/db_dependent/Circulation.t
=> FAIL: Tests fail because _FixAccountForLostAndReturned is not doing
the right thing :-D

Followed test plan, patch works as described
Signed-off-by: Alex Buckley <alexbuckley@catalyst.net.nz>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>